Aquaponics (Growing Plants With Fish Poo)




Introduction: Aquaponics (Growing Plants With Fish Poo)

I've been fascinated by Hydroponics for years. When it finally came time to play around with one, I found out about Aquaponics - a sort of symbiotic relationship between the plants and the fish. The fish provide food for the plants, and the plants clean the water for the fish. Let's see how it works!

Please bear with me, this is my first Instructable :)

Step 1: Gather Materials

I did quite a bit of reading up on Aquaponics systems before deciding on this system design. You may want to look around for ideas on how to proceed.

Materials needed:

(1) Plastic tote (for plants) $10 at the grocery store
(1) Bulkhead fitting for drain $12 at a local hardware store
(6) ft 3/8" Polyflo tubing $10 at Lowes
Polyflo fittings (all push to connect, or Insta-Tube) 3/8":
(2) 90deg elbow $4
(1) Ball valve $6
(1) Submersible Aquarium Pump* $40 at local Aquarium store (see note below)
(1) 10 gallon Aquarium $free! I've had it since I was 10 - check Craigslist
(1) Bag of Hydroton grow media $32 at a local garden shop
(6) inches of 2" PVC pipe $? This was scrap
(1) 2" PVC Pipe Cap $? Got it from my Dad
(16) inches of 1/2 PVC pipe $ Also from Dad
(1) Tube Aquarium Safe Caulking $10 at local Aquarium store.
(1) bunch of shiney rocks
(1) Something to put your fishtank on
(1) Shelf about 3-4 feet above the fish tank
(some) Vinegar
(10) gallons of water
(some) Fish I'll get to that bit later :)
Tools Needed:

- Wood Saw
- Cordless Drill
- Drill bits
- Hair Drier
- Pliers
- Scissors
- A small file
- A Sharpie marker

Notes on the pump:
Make sure it can pump water up to where your grow bed will be - the higher you pump the water, the slower the flow rate. My pump is rated for 160gph(gallons per hour) and it works pretty well pumping water 3 feet vertically. Talk to your local Aquarium guy if you have questions.

Extra notes:
Fish don't like copper or Brass. Don't use them anywhere for anything. Use plastic. Seriously.

Step 2: Connect Polyflo Tubing to the Pump

The pump that I purchased didn't have a good method for attaching a pipe or a tube to its discharge, so I got a bit creative.

Using the hairdrier, I heated the end of about 3 feet of the polyflo tube until it was soft all around.
I used a pen to flare the end of it until it was large enough to slip over the discharge of the pump.
This took a while, and a bunch of patience.
I didn't end up needing the caulking for this bit, but you may need to to make a nice seal. For me, when the tube cooled, it shrank a bit and made a nice seal.

Step 3: Install Drain on the Grow Tub

This is the bit that took the most research - how do I make a system that is simple and reliable?
Having worked in a factory before, I know that level sensors and valves and timers can find all of these great and interesting ways to fail and make huge messes.

The solution to this is the Bell Siphon. It is incredibly simple, and incredibly reliable. Perfect!
For a neat animation on how they work, check out this link:

For this system, the bell siphon consists of:
- The standpipe attached to the drain hole on the Grow Tub.
- The 2" pipe and cap acting as a "bell"

First, the toilet bowl assembly needs to be cut apart so that we are left with a 4" pipe on the end of the Bulkhead Fitting (a bulkhead fitting is a fitting that is designed to attach a pipe to a hole in a tank)

Next, a hole has to be drilled in the bottom of the Grow Tub, large enough for the Bulkhead Fitting, but not too big. Assemble the Bulkhead Fitting in the hole as shown.

Step 4: Make the Bell

How it works:

The pump is constantly filling the Grow Tub with water, but adding water slower than the drain can suck it out.

When the tub fills with water, it gets to the top of the standpipe, and starts to flow back into the Aquarium. When this happens, it sucks all of the air out of the space between the standpipe and the bell. The Bell over the standpipe maintains the siphon until the Grow Tub is empty of water.

To Make the Bell:

With the wood saw, make 8 cuts equally spaced on one end of the 2" pipe. The saw can make cuts on opposite sides of the pipe at the same time, so make one cut, then one 90deg from that, then cut each 'tooth' in half. (Too detailed?)

with the plier, grab a hold of a 'tooth' as close to the base as possible, and bend it back and forth until it snaps off. Do this to every other 'tooth' and you will be left with something that looks like the top of a castle turret. Use the file to smooth things out and make them pretty, if you'd like.

The purpose of these gaps is to let water flow into the Bell easily when the siphon starts. This will make sure that the Grow Bed drains quickly.

Step 5: Set Up the Grow Bed

I used a 1" drill bit to cut a hole in my shelf for the drain. This let me put the Grow Bed in the center of the shelf, where the weight of it would be distributed more evenly amoungst the wall brackets. Don't want it falling off the wall!

To mark the location of the hole, put the Grow Bed on the shelf where you'd like it, and put the sharpie marker inside the stand pipe, tip down. Wiggle it a bit and it will mark where you should drill your hole.

Make sure that the bottom of the Bulkhead Fitting fits through the hole, and that the Grow Bed fits in place nicely.

Step 6: Prepare the Hydroton

After doing some research on the matter, I decided to use Hydroton grow media. It is clay balls, about 1/4" in diameter. They are pH neutral and inert, which is nice, because they won't leach stuff into the water and make me adjust the pH all the time like some gravels will. It is more expensive than gravel though. In the bag, it looks just a bit like dog food. I find it a bit odd...

Hydroton has to be washed before you use it. Nothing dangerous, it is just to get rid of the dust that inevitably is generated when thousands of clay balls get jostled around during shipment. Use a pot and a strainer, clean them in the sink (or tub). I used a solution of a splash of vinegar per wash them, and rinsed them with clean water. If you don't do this, you'll get brownish gunk in your fish tank. Who needs that?

Another tip - put a strainer in your drain hole before you start. You will spill some rocks, you will have to reach down the drain to get them.

Oh, and rinse twice. There's a lot of dust. I used the 2nd rinse water from the last batch to rinse the next, but my stones still dumped a lot of dirt into the tank. Use fresh water each time.

Luckily, beta fish are quite difficult to kill in my experience, I've heard they don't mind murky water that much. Either way, I'm still doing a water change soon.

Step 7: Set Up the Tank

Locate the fish tank where you want it. It will be tough to move once you fill it with water - water is 8.34 pounds per gallon, and there will be several gallons of water used here!
My pump has suction cups on the bottom of it to keep it in place. I stuck it where the intake was as close as possible to the bottom of the tank, with the discharge facing up (it rotates!) I connected my ball valve to the end of the Polyflo that is attached to the pump. This valve is all the way open. With the Grow Bed on its shelf, two 90deg fittings make sure that I don't have to bend the Polyflo to get it into the Grow Bed. You can bend it with a hairdrier, and it'll take a bend ok, but it is irritating, and I am lazy.

Step 8: Test the Bell Siphon

To make sure everything works properly before adding rocks, set up the system for a quick test. Attach the long 1/2" PVC pipe to the discharge of the Bulkhead Fitting. This long discharge will help to keep the siphon going. Put the Bell over the standpipe.
Running pumps dry is bad. They use the water they pump to keep themselves cool. Put enough water in the bottom of the tank to cover the pump. Turn on the pump and make sure it pumps water into the Grow Bed. If not, you may need a bigger pump. Now that you know the pump works, Add more water to the tank and turn on the pump. Fill the grow bed, and look for leaks on the Bulkhead Fitting. Also check to make sure that the shelf isn't going to break. That would be bad. Once the water level gets above the standpipe, water will start flowing through this siphon. It will be slow at first, and then SLURP! speed up as the air is sucked out of the Bell. Make sure that when the Grow Bed is empty, the siphon action stops. If the pump is going too fast, it may be adding water just as fast as it is draining. If this happens, close the ball valve a bit. Mark the maximum level of the water.

Step 9: Disaster!

The Grow Bed leaks! A little investigating, and I discover that the flange at the base of the standpipe has a little flat on it. I"m guessing that this is compressing the gasket non-uniformly, and when the Bell is placed over the standpipe, it squishes the gasket just a little more - making it leak.

My solution - O rings. I bought a pack of #18 O Rings at Lowes, for $2. Placed one between the standpipe flange and the gasket, and one between the bottom of the Grow Bed and the locknut.

Why #18? Because they fit nice and snug over the threads of the standpipe.

Re-assemble, test, success!

No leaks.

One note of caution - if you find this necessary, don't over-tighten the locknut - it can 'extrude' the O-ring: The spinning action distorts the Oring, making part of it squish out. This can damage the O-ring and make a bad seal.

Step 10: Add the Hydroton to the Grow Bed

Put a screen around the bell, an inch or so off. Little rocks clogging the intake will cause a flood. Or they get sucked down into the fish tank. Fill the Grow Bed with Hydroton, 1/2" above the maximum water level.

Do another fill test while watching. Rocks are heavier than water, though Hydroton is pretty close to neutrally buoyant. The grow bed may be heavier this time. Try to notice if it falls off the wall or not. Also, make sure that the siphon starts up and stops like it is supposed to.

If the Siphon starts slurping at the end, but does not stop, use the ball valve to slow the water addition into the Grow Bed until the Siphon breaks. Monitor the system for a few hours to make sure this doesn't happen to your system.

My initial testing was done without a screen around the Bell - as a result, smaller Hydroton bits were sucked through the siphon and dropped into the fish tank. Eventually, or course, a larger one made the journey, and clogged the standpipe, resulting in a failure to begin or end the siphon.

Use a screen. Mine was pretty easy to make - I used a tall 'fill it yourself' Deli container for olives (about 6" tall, 5" across at the rim, 4" across at the bottom). I drilled a lot of 1/8" holes as close to the rim as possible, to allow water to flow in from the bottom. I cut a hole out of the bottom of the cup large enough to remove the bell, in case the drain pipe gets clogged. It would be MUCH easier to get this in place before you fill the Grow Bed with Hydroton. There can't be any Hydroton inside the screen, or it will eventually get sucked into the Bell and clog the standpipe.

Step 11: Nitrogen Cycling

Biology lesson! This is sort of important, unless you hate your fish.

Fish excrete ammonium through their gills as they breath (this is all according to my research so far - feel free to leave messages to correct me). If this builds up too much in the water, it will poison the fish. Luckily for us, there are some helpful bacteria available that like to eat ammonium. They will grow on the surface of the Hydroton. They turn the Ammonium into Nitrites. That's not very helpful by itself, since Nitrites are also not good for fish. Another bacteria will eat these Nitrites and turn them into Nitrates. Plants like Nitrates, fish don't mind Nitrates. Plants feed on Nitrates and other stuff and give us yummy food.

All of this does take some time to occur though, so if you just throw fish into this system now, they will probably get poisoned before the Ammonium-Nitrites-Nitrates cycle can establish itself. To establish this cycle, you can add 5 drops of Ammonia to your water, and turn on the system. The Ammonia will spread through the system, soak into the Hydroton, and encourage these helpful bacterial colonies to establish themselves. This does take some time though, a week or two. An aquarium store should have supplies that allow you to check these Nitrate/Nitrite levels. Be patient. Unless you hate your fish.
If you want to learn more about this stuff, check out this link:

Step 12: Add Living Stuff

You can add fish and plants now.
Commercial Aquaponics systems are sized for a ridiculous amount of fish (Almost 1lb of fish per gallon of water). To do this, they have to optimize their Grow Bed size to ensure that the water is being properly filtered. They usually also use air stones to add oxygen to the water. This extreme system is not necessary, you can get away with a lot less. I'm using a betafish for my system to begin with, I'll add some goldfish in a few weeks. The amount of oxygen added by the Auto Siphon cycling constantly should be enough to oxygenate the water. Add fish to the system slowly, so that you don't upset the Nitrogen Cycle in the tank.

For plants, you can start them in Rockwool, and then transplant them into the Hydroton, or you can try to start the seeds directly in the Hydroton. The rockwool may promote root rot later on, so I'm going to try direct sowing, but I hear it is more difficult.

Step 13: Things to Add Next

1. An Overflow
In case of a clog in the drain, I really ought to add an overflow to the Grow Bed. It would require another Bulkhead fitting, installed above the Hydroton, on the sidewall of the Grow Bed. Polyflo tubing would direct any water back to the tank. The plants will get flooded for a while, but the pump won't run dry, I don't get 5 gallons of water on my floor, and the fish get to stay wet.

2. A lid for the tank.
I think my cat is going to either:
a. Accidentally go swimming
b. Eat Se�or Fish-Fish (his actual name, by the way)

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    12 years ago on Introduction

    great instructable, I definately have to try this since I have an empty tank in my closet and an already established fish tank in my living room. The ammonia in the fish tank comes from the fish excrement (urine and feces).  Now a thought on your process, since I have an already established fish tank, and some out there might, it would be a great idea to use the water from that fish tank that you take out during a water change to get your healthy bacteria started.  also to clear uup the water a bit maybe try having the water from the plant container actually run through a fish tank filter to clear the water up a bit so you keep your fish happy.  using a carbon filter shouldn't affect your plants and it would sure help to be able to see your fish more clearly.

    Average aquarist
    Average aquarist

    Reply 2 years ago

    The design I am working on uses 2 forms of filtration, the plants and a normal filter in a small bin with an oxygen stone that then drains into the tank


    Reply 11 years ago on Introduction

    Using the water from an existing aquarium is a good idea! There's bound to be beneficial bacteria in there to kick start the process. As far as the carbon filter goes, it may help with water clarity, yes - I personally have not run both at the same time. Good luck!


    8 years ago

    hey what do you do about all the fish poop left at the bottom of the tank?

    Average aquarist
    Average aquarist

    Tip 2 years ago on Step 11

    You can also add 1 or 2 medium shrimp (like in ththe frozen fish section of the grocery) in a mesh bag into your tank to cycle it. Let them deteriorate for a few weeks and test the water. If it is good, take them out, clean any debris from the rotted shrimp out of your tank, do a water change and add in fish


    6 years ago on Introduction



    7 years ago


    10 years ago on Introduction

    If this isn't a chance for someone to become rich I don't know what is. Why hasn't anyone developed a self contained unit to make this happen! I am so tired of seeing people rig this from scratch (I applaud their efforts though!) We should have about a dozen options by now of different auquaponic systems for our homes. If I had the money to make it happen I would, but I don't. I would save up to buy one as I think would many many other people. If you add a solar panel connection that you put on the roof that powers the filter and everything else you would have something amazing! There should be one in every home.


    Reply 7 years ago

    Electric Bla
    Electric Bla

    Reply 10 years ago on Introduction

    Actually, the folks at GardenPool do sell a kit for a 'shelfponics' setup they put together. They have a nice article on how it's made and how to put one together yourself.

    Essentially, it's one of those cheap plastic fit together type shelves with the upper actual shelf pieces flipped upside down to hold water. With some plywood reinforcement the bottom shelf can hold a full 10g tank, and the rest of them hold growing medium. Some cut holes and tubing later you've got a system with a surprising square amount of growing footage for usually under $100 (assuming it's all bought.

    It's a freestanding piece too, so it won't tear down any of HoboWhisperer's drywall either! :D

    there are units for personal as well as commercial use that work great, look under cropking on the net to find some of them


    11 years ago on Step 13

    It is now about a year after this system was built and it has been decommissioned (sadly!).

    The shelf that the tank was mounted on was starting to pull out of the wall. Apparently when drywall anchors are rated, it is for xx lbs (in my case 80 lbs each) pulling straight down. The shelf brackets ended up pulling out on the upper drywall anchors and they began to slide out! I propped up the shelf with books for a while, but eventually my wife yelled at me and I took it down :). I would recommend that anyone thinking about this sort of thing should screw their shelf brackets into studs, not use drywall anchors.

    A challenge that I WAS able to overcome was an invasion of fungus gnats. They look a bit like fruit flies, but they are not as good at flying. They hung around the planter all of the time. I tried flypaper and vinegar+water (works for fruit flies)but those did not work. I didn't want to add insecticides to the system, because of the fish, but I ran out of options. I ended up adding Bt to the water. Bt is harmless to people and (apparently) fish. It works by fooling insect larvae into thinking that they are not hungry, so they stop eating and die. It takes a few weeks for the adult flies to die and for all of the eggs to hatch and starve, but it did clear up the infestation. It also turned the water brown, which I was not able to ever get rid of. After decommissioning the system, I added a charcoal filter to the system and the brown color went away within a day or two.

    It was a fun project!


    11 years ago on Introduction

    Hobo whisperer, for some reason my siphon won't kick in. I've replaced my bell with a clear one so I could see what is going on, and for some reason it's not forming a vaccume when full. Any suggestions?


    Reply 11 years ago on Introduction

    Here are some formulas for #s of fish and tank size:

    Seems the rule of thumb is 1" of fish for every gallon of water and about 3 gallons of water for every cubic foot of growing space.

    I suspect there are others that get it done with other sized tanks and different amounts of fish, though.


    Reply 11 years ago on Introduction

    I know that my system would stop syphoning when my pump flow rate was too low. This would happen when the water level in my fish tank was too low - the lower the fish tank water level, the harder the pump had to work to get water up to the grow bed (which means slower flow rate). I know there are some other instructables with more expertly designed bell siphons - I'll take a look around and see if I can find a good link. Good luck!


    Reply 11 years ago on Introduction

    What I ended up doing is putting a small piece of pipe inside the first elbow joint under my grow bed. This caused a step down and fixed the problem. HOWEVER your advice does help because when the water gets low the system does have trouble cycling. It does kick over, just takes longer. I imagine if I let it get too low it will hinder the cycling all together. Thanks so much for the reply!


    11 years ago on Introduction

    Judging by the fact you are still responding to comments, this went well? I am curious as to the amount of fish you need to plants to get a good equilibrium as I was considering doing this for just a few plants and have usually only seen larger applications. What did you grow? How did they turn out?


    11 years ago on Step 3

    in my aquaponic aquarium filter, i cut holes in the sides of the toat the plants grow in, and have that toat sitting inside a slightly larger one, with a hole in the bottom. it drains directly out the hole in the bottom back into the aquarium, through a hole i cut in the lid. it saved on buying parts and there are fewer moving parts that could fail and flood my appartment


    12 years ago on Step 13

    Good info, you can learn more for your aquaponics system at . It's a forum where you can discuss your system. I'd be careful about using goldies though, I prefer Guppies unless you intend to have some eating fish like tilapia in the future. the guppies have fry, the betta and the larger guppies will eat the fry, and you'll save on fish food ;) A lot less cleanup on the bottom of the tank that way, You've got a 10 gallon tank from the looks of it, you could have a few guppies in there without a problem and if the guppies end up overwhelming you, you can always give some of them away to the neighbor kids and drive their parents nuts! lol