small indoor aquaponics system

Complete Indoor Aquaponics – Start to Finish

Introduction: Complete Indoor Aquaponics – Start to Finish

Aquaponics is the combination of growing plants in soilless medium as seen in hydroponics, and raising fish (aquaculture). Together they provide the perfect partnership for optimal growth. The fish provide a continuous supply of organic fertilizer for the plants, and the plants clean the water for the fish. At the same time, aquaponics minimizes water waste due to it’s perpetual recycling of the water in the system. Aquaponics has been successfully used in areas of the world effected by drought, pollution, and even lack of farmable land (such as cities). Many people have been interested in aquaponics, but are unsure of where to start or are nervous about getting started. In this guide I will take you from start to finish, and show you in detail how to build your own aquaponics system for indoor use. Such systems are perfect for those interested in growing their own food, but don’t have the land or environment necessary to do so. Let’s get started.

Step 1: Aquaponics Basics

Before we begin constructing our aquaponics system, it’s important to have a basic understanding of how everything works. First, the parts of the system:

Fish Tank – The fish tank is exactly what it sounds like. This is where the fish reside. It can be anything from a 55 gallon barrel to a swimming pool. The fish tank should be made of non-toxic materials, and large enough to meet the needs of your fish.

Grow Bed – The grow bed is where your plants will grow. The grow bed should also be made of non-toxic materials, hold water, and be strong. The grow bed should be deep enough to sustain proper root growth for your plants; ten to twelve inches deep is the standard here. It will be filled with grow media to hold the plants and allow roots to grow.

Ebb and Flow (Flood and Drain) – This is the type of aquaponics system I will be using in this instructable. This type of system floods the grow bed, and then drains through a siphon providing nutrient rich water and oxygen for the roots.

Things to consider before building your indoor aquaponics system:

When designing your own system you will want to consider several things. First where will your system reside? Water weighs 8.34 pounds or 3.78 kilograms per gallon. Multiply that by the total volume of your system to find the total water weight. In the example here I have 55 gallons in my fish tank which is about 459 pounds or 208 kg. The grow bed will contain grow media which is also quite heavy. Consider your system could weight up to 1000 pounds or more. You will want it placed in an area that can sustain such weight.

Other things to consider is the water your system holds. Should your system fail and spill of it’s contents on the floor what will that look like? Will 55 gallons of water destroy the area your system resides in?

Since this system is designed to be indoors, the environmental conditions can be controlled to an extent. Water temperature, light, and humidity are important factors to consider when selecting plants and fish. Technically speaking, you could be living in Canada and grow bananas in your aquaponics system. The right conditions will need to be created, but by building your system indoors these conditions can be met. Consider the power requirements this might need when selecting your plants and fish.

Step 2: The Grow Bed

The grow bed I built here is constructed of plywood. The inside dimensions are 24″x 36″x 10″. I drilled two holes in the grow bed. The first hole is in the bottom for the siphon. This hole is big enough for a 3/4″ male pvc adapter to fit into. The second hole is towards the top of the grow bed. This hole is a fail safe. If the siphon fails for any reason and the grow bed continues to flood, this hole provides an escape for the water to flow back into the fish tank rather than all over the floor. I cut mine big enough for a 1/2″ piece of pvc pipe to fit into.

This grow bed is made out of plywood so it will need to be coated with a non-toxic water proof covering before it can be used for your indoor aquaponics system. For this I used Flex Seal . Flex Seal is great for water proofing any part of your system you don’t want to get wet, and once cured, is non-toxic and non conductive. It takes 24 hours to cure, so plan ahead and take your time with this step. Make sure you cover every part of your tank to ensure proper water sealing; any small hole left uncovered could destroy your grow bed when exposed to water over time.

Step 3: The Fish Tank

For my indoor aquaponics system I’m using a 55 gallon tote . They’re relatively inexpensive, water tight, and non-toxic. They do expand and bulge out when water pressure is applied to the walls so I had to construct a frame to keep it from breaking. I built some plank supports on top of this frame to support the grow bed. Make sure these planks are at least 4 inches tall to provide enough clearance for the plumbing coming from the siphon to the fish tank.

Step 4: The Siphon

A bell siphon is used in ebb and flow aquaponics and hydroponics systems in order to regulate the flow of water. In an ebb and flow (also known as flood and drain) system water is pumped into the grow bed. At a specific point (usually 2 inches below the surface) the water drains via the bell siphon. When the water reaches the bottom you will hear the classic gurgle indicating the end of the drain phase. The process will then repeat itself over and over again. The bell siphon is such an important part of any ebb and flow system that getting it right is crucial.

Parts and Tools needed to make a Bell Siphon:

Gravel Guard 1 – 3″ PVC pipe (approximately 12″ long)

Bell Dome 1 – 2″ PVC pipe (approximately 10″ long)

1 – 2″ PVC cap Bell Siphon

1 – ¾” PVC pipe (approximately 6″ long)

1 – ¾” to 1 ½” bell adapter

Grow Bed Connections 1 – ¾” Male adapter (thread to slip)

1 – ¾” Female adapter (thread to slip)

2 – #18 o-rings Drain Pipe 2 – ¾” PVC pipe 4″ long


Preparing the Dome and Guard

I created a guide that you can use to make clean and equally spaced holes around the bottom of your gravel guard and bell dome. First download the “Bell Holes Guide” document (link to dropbox) and print it. You will likely get an error message saying, “The margins of section 1 are outside the printable area of the page. Do you want to continue?” Click Yes. Cut out the two guides, wrap each guide around the bottom of your PVC pipes (the 3″ gravel guard, and the 2″ Bell dome), and tape them in place. Use the guide to drill ⅛” holes around the bottom of each pipe. Remove the guides and clean up any leftover PVC dust or tags.

Building the Siphon

Follow the Bell Siphon Diagram to put the siphon together. Start with the male and female adapters. Take the male adapter and slip a #18 o-ring over the threads. Insert the adapter through the access hole in the grow bed. Slip another #18 o-ring over the top of the male threads. Screw the female adapter to the male adapter (no jokes here folks) making sure you have a tight connection. It’s not necessary to get the tools to tighten it, hand tight or even slightly less than is fine (you’ll be checking for leaks later anyways so it’s not necessary to overdue it). Slip a 6″ piece of 3/4″ PVC pipe into the female adapter (The diagram says this is 4″, start with 6″ and check the water line when you’re done. If the water line is too high, make a note and adjust this pipe as needed). Slip the 3/4″ to 1 1/2″ bell adapter on top of the 3/4″ PVC pipe . To create an effective drain flow it is important that the opening of the Bell is double the size of the pipe (¾” * 2 = 1 ½”). Slide the PVC Bell Dome (Again, start with 10″ and adjust if the water line is too high) over the drain pipe, and the PVC stone guard over this. For the underside of the grow bed slide a piece of ¾” pipe into the bottom of the adapter. Slide a ¾” PVC 90 into the bottom of this pipe, and from there another ¾” PVC pipe. Depending on the location of the fish tank you will need to size these last two pipes appropriately.

Test it out

After you have your bell siphon put together feel free to test it by filling the tank. Take note of the water level where the siphon starts, and especially the max height of the water. The max height of the water should be 2″ below the grow media surface. If you need to adjust any pipes now is the time to do it. For example, if your water line is an inch above the mark, take an inch off the top of the siphon pipe, and an inch off the top of the bell dome.

Step 5: Ebb and Flow Automation

Automated Water Pumps

One thing I really wanted to automate was the pumps. In an Ebb and Flow system you would normally need to watch how long it takes to fill up the grow bed until it begins to drain down the siphon. You would then set your pump to a timer so that your grow beds aren’t sitting in too much or too little water for too long. This is tedious, and the fillup time is variable.

To automate the process I’m using an Arduino Uno Microcontroller to receive an input signal from a Hygrometer (moisture sensor). Depending on the signal (wet or dry), the arduino will turn the pump on or turn it off. In action the pump will be on until the grow bed fills up and the siphon activates the drain process. When the water drains, the hygrometer will pick up on the moisture (100% in this case) and tell the arduino to shut off the pump for 30 minutes. After this dry cycle, the arduino checks the hygrometer for moisture (it’s been dry for 30 minutes) and turns the pump on again if it’s dry. This takes care of the variable flood times, and ensures a proper flood and drain cycle.

Parts for the flood and drain automation system



Setting it up

Follow the instructions here to setup your arduino for the first time. Once you have the arduino software on your computer you can download the sketch for the automated ebb and flow system here. Once you’ve downloaded the ebb and flow sketch you can open it and upload it to your arduino board. If everything has uploaded successfully you can begin hooking up all the hardware to make the magic happen.

The hygrometer sensor checks for water in the drain pipe. Because of this we need to make a module containing the hygrometer that connects to the drain pipe. I did this by inserting a ¾” PVC T in line with the siphon drain pipe. I made a module out of a small piece of ¾” pipe with a ¾” cap on top. The hygrometer is contained within this end cap with two holes to allow the sensor wires to connect to the arduino. To prevent any leaks or damage you can cover the holes and secure the hygrometer inside with non-toxic silicone or flex seal.

Step 6: Flooding


Flooding the grow bed is easy enough. I used 1/2″ PVC pipe going from the pump to the grow bed. Between the pump and the grow bed I created a branch that supplies water back into the fish tank. This creates a break in the water which provides oxygen for the fish.

You may need to fool around with various pvc pieces to fit the pvc pipe into the pump. I used a brass barb hose splicer (sanded one end of the barbs) to fit into the pump hole. On the other end I fit a small piece of 1/2″ pvc which I made water tight with flex seal. Then I fit a 1/2″ pvc couple over the 1/2″ pvc pipe. The delivery pipe can then slip into this couple.

Once you’re able to attach the intake pipe to the pump, find a good place for you pump to sit in your fish tank. Then attach the intake pipe to the pump and let it rest in a position to allow water to flow into the grow bed. I secured the flow intake pipe with a plastic clip found at any hardware store in the plumbing section.

Step 7: Grow Bed Media

After you’re sure the plumbing is working properly it’s time to fill the grow bed with grow bed media. When choosing media there are several things worth considering. Some of the biggest factors to consider are cost, weight, pH neutrality, and surface area. Here is a short list of some of the most common media used in aquaponics.

Hydroton Clay Pebbles – Clay pebbles are a great choice for grow media. They are pH neutral, easy on the hands, light weight, have a large surface area, and don’t break down. This media choice is traditionally what you will find in most aquaponics systems. One downside to hydroton clay pebbles is it’s expense. They are by far the most expensive choice.

Lava Rock – Lava rock is another great choice because they are pH neutral, light weight, and have a large surface area. They are cheaper than clay pebbles, and you can often find it for free if you know where to look. The downside to lava rock is they can be rough on the hands and roots if you handle them too much.

Pea Gravel – The biggest advantage to pea gravel is it’s much cheaper than the other alternatives. That said, pea gravel comes with many problems. Pea gravel has a smaller surface area than other choices, is heavier, doesn’t hold moisture very well, and can have negative effects on your systems pH.

As you can see from the pictures, I decided to use lava rock in my own system. From my own personal experience this is a very good choice for aquaponics systems. An important step to take before adding the media to your grow bed is washing/rinsing it thoroughly. I used a 5 gallon bucket to do this.

Take a 5 gallon bucket and drill several holes in the bottom for sediment and dirt to drain out of. Use a garden hose to spray off the media while you separate the clean media from the dirty media. Once the media is clean from dust and dirt, add it to the grow bed until you’ve filled it completely.

Step 8: Grow Lights

Plants need a special kind of light to grow properly; you can’t just turn on a lamp and call it good. You’ll need specific lights called grow lights for your plants to grow properly. There are all kinds of grow lights out in the market. You can find anything to meet your needs on Amazon and even some basic models at Walmart.

You can actually set your Lighting to an AC timer since it doesn’t require any input. Grab an AC timer from the store (after you’ve paid for it obviously) and set it to 16 hours on, and 8 hours off. To save yourself on energy costs, make sure the off cycle is happening during your actual peak power times. For most of us this is between 2PM and 8PM on weekdays, and 7AM to 2PM and 8PM to 10PM on weekends.

Step 9: Cycling Your Aquaponics System

You have your fish tank, the grow bed is filled with media and is ready to go. The pump and plumbing is working perfectly. Everything is looking good and you’re ready to get things growing! This is an exciting moment, but don’t be too quick to rush into growing just yet. The final stages of setting up your aquaponics system is making sure the chemistry is right. To do this we need to cycle the system, a process that takes ten days to a month to do.

Cycling is the process of establishing a healthy system that converts fish waste into healthy plant food (nitrates) effectively. To do this, your system needs to establish a healthy level of bacteria. In this process you will need a test kit to track water pH, ammonia, nitrites, and nitrates. You will also want to test water temperatures as well. Don’t worry, you don’t need a degree in chemistry to do this. The process is very simple if you follow the steps and track the data religiously.

For this process you will need an aquarium test kit. I’m using the API Freshwater Master Test Kit , sold on Amazon or at pet stores. You will also need a thermometer to check water temperatures. For this I used a cooking thermometer because I had it on hand already. You will also need ammonia to jump start the process. It must be pure ammonia. Look for this in the cleaning supplies section of your grocery store. Make sure it is pure; you will find two ingredients in it, water and ammonia. Make sure it doesn’t have any added scents or coloring; I can’t stress this enough.

Once you have everything you need you can start the process of cycling your aquaponics system as follows:

  1. Measure out a small amount of ammonia (take note of how much was added) and add it to the tank until you obtain a reading 5 ppm. Make sure you are tracking temperature, pH, nitrites, and nitrates from day one.
  2. On a daily basis, add that same amount of ammonia and continue to measure and record temperature, pH, nitrites, and nitrates until the nitrites show 0.5 ppm.
  3. Once nitrites show 0.5 ppm, add only half the amount of ammonia you have been adding for the past couple of days. Continue to do this daily and remember to keep tracking your data.
  4. Once nitrates appear ( between 5 and 10 ppm), and the nitrites have dropped back to 0, you can add your fish and stop adding ammonia to the system.

Feel free to plant in the grow bed during the cycling process. Your plants will show some deficiency at first, but will help in getting your system up to appropriate levels to self regulate. After the cycling process your plants will begin to flourish. Fish should be added after the cycling process because the levels of ammonia during the process will more than likely kill them. Once the fish are added they will provide the ammonia naturally.

Step 10: (Trans)Planting

Adding plants to your indoor aquaponics system is very easy. You will need a plant that has already established at least a small root system. Remove the plant from it’s current home and wash off as much dirt as possible. In the grow bed, create a small hole by displacing the rocks in the area you want to establish your new plant. Place the plant in the hole and replace the media that was removed to make the hole. You can adjust the way your plant is sitting in the hole so that it’s not falling over by adjusting the rocks that hold it up. The roots will grow and establish themselves in the grow bed in a few weeks time.

Step 11: Fish

In your aquaponics system, the fish will be providing the fertilizer for the plants you will be growing. Because of this, you will want to make sure they are happy and healthy. Some things to consider when choosing a fish are the size of the fish, pH tolerance, temperature tolerance, oxygen needs, dietary needs, and whether you yourself are planning on harvesting the fish down the road. I’ve provided a list of common fish to use in aquaponics and their requirements (see photos).

In my own system I decided to use Channel Catfish. I went with catfish for several reasons. First, I will be harvesting my own fish and I particularly enjoy the taste of fried catfish. Second, catfish have a high tolerance for colder climates and lower levels of oxygen; they are a very hardy fish. Third, they are extremely easy to feed. Catfish are omnivorous and require a good balance of plant and animal protein as well as plant based nutrients and amino acids. The cheapest food out there without sacrificing nutritional requirements I have found is cat food. It can’t get any easier than that. On a side note, cat food is shaped and packed in a way that would make it optimal in an Automatic Fish Feeder .

You don’t have to feel limited by fish if you would prefer a different route. Other aquatic animals known to have been used in aquaponics include such species as turtles, ducks, freshwater shrimp, worms, and crayfish. If you would rather use one of these creatures instead of the traditional fish then go for it.

Step 12: Supplementing Your System

For the most part, your new aquaponics system is self sustainable, provided you feed your fish frequently and check pH, nitrite, and nitrate levels every now and then. That being said there may come a time when your plants need a little extra boost. In such times I have a few tricks up my sleeve that are pretty effective. This step is completely optional, and is “for your information” only.

Banana Tea – Banana tea is an organic potassium fertilizer that aids plants during times of flowering and fruiting. This is easy to make at home, and is completely safe to add to your aquaponics system. To make banana tea, chop up five banana peels and place them in a pot with one liter of water. Put the pot on the stove and boil for 15 minutes. Discard the banana peels and save the remaining water by straining the mixture over an empty container. Finally, add an additional two liters of water to the banana tea.

Egg Shell Powder – Egg shell powder can help remedy calcium deficiency in your plants and raise pH levels. Save any egg shells you may normally discard until you have 12 – 24 egg shells. Make sure they are rinsed properly and allow them to dry. Put them in the microwave for a couple minutes to destroy any bacteria growing on the egg shells. Put the egg shells in a blender and blend them to a powdery consistency. Use this in your system as needed by sprinkling it into your grow beds.

Seaweed Extract – Seaweed extract is another great additive to give your plants an added potassium boost along with other trace elements. First gather seaweed from the beach or shore and rinse it thoroughly. Fill a five gallon bucket with water (approximately 3/4 of the way up) and soak the seaweed in this bucket. Stir the seaweed every three to four days until you can no longer smell ammonia coming from the mixture. After a few weeks it should be ready to use. Discard any solids and add water to the remaining liquid to dilute (3 parts water to 1 parts seaweed extract). Use as needed by pouring it into your system.

Complete Indoor Aquaponics – Start to Finish: Aquaponics is the combination of growing plants in soilless medium as seen in hydroponics, and raising fish (aquaculture). Together they provide the perfect partnership for optimal growth. The fish provide a continuous supply of organic fertilizer…

Build a Mini Aquaponic System

Build a Mini Aquaponic System

Below is an article Rebecca Nelson wrote to help students build a mini aquaponic system to demonstrate the science of aquaponics.
Students, have fun and enjoy aquaponics!

A mini aquaponic system is an excellent means of demonstrating aquaponic principles and the nitrification cycle in a recirculating aquatic environment. Following are instructions for building a small system that is ideal for a teacher, students or hobbyists who want to get a start in aquaponics. If you are looking for a complete kit, be sure to check out our Clear Flow Aquaponic Systems®

What You’ll Need

Following is a list of the parts you’ll need to build a mini aquaponic system. The next section, Component Explaination, describes and explains each of these components and includes recommendations for alternative items and specific products.

  • A tank for the fish: 3-20 gallon, glass or plastic container ($10 – $30)
  • Gravel: 2.5 lbs. of gravel for every 5 gallons of water in the fish tank ($5 – $15)
  • Water pump: 3-4 watt pump capable of lifting 18” – 54” at 30 – 100/gal/hour (small circulation or fountain pump is ideal) ($25 – $50)
  • 3 ft. of plastic tubing that fits the outlet on your water pump ($1 – $2)
  • Aquarium air pump sized for the number of gallons in your fish tank ($10 – $25)
  • Air stone (1” – 3”) ($2 – $10)
  • 3 ft. of air tubing to connect the air pump to the air stone (must fit the air pump outlet) ($ 1)
  • Grow Bed: must sit on top of fish tank and be 3” – 8” deep ($5 – $20)
  • Growing Medium: enough pea gravel, perlite, coconut coir, expanded clay pebbles or peat moss to fill the grow bed ($5 – $10)
  • pH test kit and, depending on the pH of your water, pH down or pH up ($10- $50)
  • Fish and plants

Tools Required

  • Drill with 1/4” or 3/16” bit and 1/2” bit
  • Scissors
  • Electrical tape

Component Explanation

A tank for the fish

The fish tank can be a glass or plexi-glass aquarium or you can use any other clean container that holds water: for example, a plastic tub, bucket or barrel. We recommend anything between 3 – 20 gallons, although, you can go with a larger tank if you have the space. Small, clean plastic amphibian cages, available in most pet shops, make an excellent mini-system. They hold about 3 gallons and are quite inexpensive.

The standard sized fish aquariums of 10 and 20 gallons are also reasonably priced. The larger the tank, the larger grow bed area you can support. As a general rule, you can support 1 – 2 square feet of growing area for every 10 gallons of fish tank water.

Gravel for tank bottom

The gravel serves as a home to the nitrifying bacteria that convert ammonia to nitrite and then to nitrate, which can be used by the plants. Most pet stores carry natural or colored aquarium gravel. The individual pebbles are about 1/8” in size. Be sure to wash the gravel thoroughly before using it because it is often dusty. Unwashed gravel will cloud your tank water.

Water pump and tubing

A small water pump is used to pump the water from the fish tank to the grow bed. After the water is pumped into the grow bed, it gravity-feeds back to the fish tank. You’ll need enough tubing to go from the outlet on the pump to the top of your grow bed and form a circle within it.

Air pump, air stone and tubing

You need an air pump to blow air into the tank water for both the fish and the plants. Tubing connects the air pump to an air stone at the bottom of the tank. The air stone breaks the stream of bubbles coming from the air pump into micro-bubbles, which greatly increase the oxygenation in the water.

Grow bed

The grow bed, which sits on top of the tank, must be slightly larger than the length and width of the fish tank. The grow bed is filled with a growing medium that the plants grow in. A plastic Rubbermaid container, a garden planter or other container that will sit on top of the tank will work fine. The container should be between 3” – 8” deep.

You can use a plastic tub or, for a very nice looking unit, build one out of plexi-glass and seal it with a non-toxic, silicone glue. If you build the grow bed, you can accommodate an aquarium light by making a cavity in the grow bed that the light can slide into. If you are using some other kind of container, a light can sit just behind it if there is room.

Growing medium

A growing medium is a porous, chemically inert material that holds the plant roots and maintains moisture. Examples include: perlite, expanded clay pebbles, peat moss, pea gravel and coconut coir. You need enough to fill your grow bed.

Fish and plants

In an aquaponic system, the fish provide the nutrients the plants need and the plants purify the water by consuming those nutrients.

Optional Components

Aquarium heater (for tropical fish)

Most gardeners or aquarists setting up an aquaponic system choose ornamental fish for the tank and most ornamental fish originate in tropical waters. A tank temperature of 78 degrees F will need to be maintained for tropical fish. Two kinds of aquarium heaters are available: submerged and tank-side mounted. Either will work, but be sure the heater you choose is sized for the number of gallons of water in your fish tank. If the aquaponic system is placed in an area where the air temperature is maintained between 70 – 76 degrees F or, if you choose cool water fish goldfish, you do not need a heater.

Light for fish tank

Most aquariums have a florescent light so you can see the fish and monitor their health. You can add one if you’d like, but it is not a necessity.

Grow light for the plants

If you establish your system in an area with low light levels, you may need to add artificial light for healthy plant growth. Keep in mind that bright light will quickly encourage algae growth in the fish tank. You should try to point an artificial light in a way so that it does not directly penetrate the fish tank. If you do have rapid algae growth, you can scrape the interior walls of the fish tank or buy a plecostomus, a fish that eats algae. If the grow bed is in a windowsill with bright sunlight, in a greenhouse or planted with plants requiring low light levels, a grow light isn’t necessary.

Assembly Instructions

Step 1
Thoroughly wash the gravel and place in the bottom of the fish tank.
Step 2
Drill 1/8” or 3/16” holes in the bottom of the grow bed every 2 square inches so the water can drain into the tank. In one of the back corners of the grow bed, drill a 1/2” hole for the tubing from the water pump to pass through.
Step 3
Place the water pump in the fish tank then set the grow bed on top of the tank. Feed the tubing from the water pump through the 1/2” hole. Leave enough tubing to extend about 3/4 the height of the grow bed and to loop around the inside of the grow bed. Cut off any excess tube and fold the end over. Seal the folded piece with electrical tape.
Step 4
Fill the grow bed with the growing medium to just under the top of the tube.
Step 5
Puncture small holes every 2 inches in the section of tubing that loops in the grow bed.
Step 6
Cover the loop of tubing with an inch or two of growing medium.
Step 7
Fill the fish tank with water. Plug in the pump to ensure that the water is pumped into the grow bed, trickles down through the growing medium and continuously back into the tank. Depending on the size of your tank, grow bed and pump, you may have to adjust the flow.
Step 8
Connect you air pump to the air stone with the air tubing. Place the air stone in the tank and plug in the air pump. A steady stream of bubbles should rise through the water, providing fresh air.
Step 9
Check the pH of your water using litmus paper, a pH test kit or pH meter. Limtmus paper and inexpensive pH test kits are available in most hardware pool supply stores. The ideal pH is 7.0 for an aquaponic system. If it is higher than 7.2 you should lower it with a “pH down” product and if it is lower than 6.8 you should raise it with a “pH up” product, both of which are available from aquarium stores.
Step 10
Allow the unit to sit for 24 hours to be sure all chlorine has dissipated from the water. If you want to stock your fish right away, you’ll need to add a chlorine remover, which is available from aquarium shops and pet stores.
Step 11
Add your fish to the fish tank. Initially, you should lightly stock your tank with no more than 1/2” of fish per gallon of water. Once your system has been established for over a month you can increase to fish density to 1” per gallon of water.
Step 12
Ideally you should wait approximately 4 weeks to add plants to your system, but if you are eager to plant it, add just a few plants or seeds and increase plant density in a month or so when your system is well established.

Fish and Plant Selection

In selecting your fish, choose hardy species like goldfish, guppies, angelfish and other common varieties available from your local aquarium or pet store. Most desktop aquaponic gardens do not include food fish because there isn’t enough space to grow them to maturity. If you do want to raise food fish or a local species, be sure to provide adequate water temperature and feed.

A desktop aquaponic garden will support most varieties of house plants, lettuce, spinach and herbs. Ideally, you should start your plants from seed in a grow cube (also called jiffy cubes) or loose in the growing medium in your grow bed. Very small seeds can be sprouted by placing them between two paper towels that are kept warm and moist. You can also transplant plants from an existing hydroponic system with good results.

If you must transplant from soil, thoroughly wash away all of the dirt surrounding the roots and wash the leaves being sure to remove any pest insects.

You will have the most success with leafy vegetables like lettuce, spinach and herbs or houseplants such as anthodium, dracaena, dieffenbachia and philodendron.

You can also plant aquatic plants in the fish tank. They will provide a more natural habitat for the fish and aid in purifying the water.

Nitrification Cycle

Fish excrete ammonia in their wastes and through their gills. In sufficient quantities ammonia is toxic to plants and fish. Nitrifying bacteria, which naturally live in the soil, water and air, convert ammonia first to nitrite and then to nitrate. In your aquaponic system the nitrifying bacteria will thrive in the gravel in the fish tanks and in the growing medium in the grow bed. Nitrate is used by plants to grow and flourish. The plants readily uptake the nitrate in the water and in consuming it, keep the levels safe for the fish.

System Maintenance

The only daily input in this system is fish food. With any aquarium, frequent small feedings are better than fewer large feedings. Unless you have a really large tank, a pinch of food is all it takes. You should never feed more than the fish can completely consume in 5 minutes. Most tropical fish will be fine with a dry flake fish food but occasionally varying their diet with brine shrimp or blood worms will definitely keep them healthier and happier.

The water level in the tank will slowly decrease as some water is absorbed by the plants and some evaporates. Every few days you should refill the tank to the top. About once a month a 10 – 15% of the tank water should be siphoned out and replaced with fresh water.

Experiment Ideas

An aquaponic system is an excellent tool for experimentation and proving or disproving a hypothesis. Following are four theories and experiments that can be done to prove each.

Theory 1

Although an aquaponics system will produce good plant growth, the hydroponic system with precisely measured nutrients will produce faster growing, higher quality plants.

Experiment 1

Set up a hydroponic system and an aquaponic system. Monitor and document which one best supports plant growth.

Theory 2

A healthy aquaponic system has ample nutrients for leafy crop growth, but fruiting plants will be lacking sufficient quantities of certain elements.

Experiment 2

Plant a leafy crop such as lettuce and a fruiting crop such as tomatoes and monitor to see which one does best in aquaponics.

Theory 3

A pH of 7.0 is the best for an aquaponic system. At a lower pH, nitrification slows down and the water quality will be reduced, stressing the fish, and at a higher pH the plants will be stressed.

Experiment 3

Set up three aquaponic systems. Run each at a different pH, one at 6.0, one at 7.0 and one at 8.0. Observe and document the plant growth and fish health at varying pH levels.

Theory 4

Denser fish populations will support more plant growth due to increased fish waste and nutrients in the water.

Experiment 4

Set up two aquaponic systems, stock one with 1” of fish/gallon of water and the other with 1/2” of fish per gallon of water. Observe the difference in plant growth.

Use this step-by-step guide to build a mini aquaponic system. This basic system can be used in a classroom to demonstrate aquaponics.