Windowsill Aquaponics System




About: I enjoy coming up with ideas for things and then trying to build them. It brings me pleasure.

I wanted new pets, but I don't like having to do a lot of taking care of them work. I also like growing things. The union of the two was an aquaponics system. The problem ... I live in New York City. And, to paraphrase Genie in Aladdin, "Infinite energy in the city, but itty-bitty living space!"

All aquaponics systems I saw had large spaces. Even the one that had the big Kickstarter and is sold in Home Depot is about as space efficient as a Humvee--it is a large cube and wouldn't be possible to fit in my apartment. So, I decided that the ideal system would be small enough to fit on a windowsill (so everyone could enjoy it) and also be self-maintaining.

For the unaware, an aquaponics system is one in which fish are fed, then the water from the fish habitat pumps through a container in which plants grow, the plants in the container then use the fish waste in the water as nutrients and grow meanwhile cleaning the water and acting like a natural filtration system, which then returns the water to the fish tank, clean and ready to start the cycle anew. To make it self-sufficient I added an automatic feeder I had left over from red painted sliders we used to have (we set them free).

Gold fish are ideal small tank aquaponic starters as they can handle pretty varied environments and also do not need water heated to a specific temperature to survive. Given that this system is meant for a windowsill, algae feeder fish are also beneficial to include.

PS I am entering into the Indoor Gardening Contest, please please please vote for this Instructable, if you like it. :-)

Step 1: Materials

I ended up going through a number of variations. I tried a bell syphon setup, but with such a small system, drainage was too slow and the system lagged. I ended up going with a constant flow timed drain system where my pump shuts off for 15 min out of every hour. [Please disregard the extraneous items in the pictures as some were used initially but then removed/replaced during trial runs of the system.]

(1) Tank (long beta tank), dimensions: 18" x 5" x 7" (Deep Blue Beta Tank), 2.3 Gal (~$35)
(2) plastic transport tank/cage (Petland Discounts, $6)
(3) automatic feeder (had from previous pet)
(4) aquaponics small water pump (66 GPH, submersible, from PonicsFarm via Amazon, $11.99)
(5) PVC piping (2 x 5.5" long w/1" diameter, 1" corner, 1" coupler)
(6) tubing (1/2") [to connect water pump with corner spout)
(7) 1/2" to 1" tubing to PVC converter [spout piece]
(8) 1 plastic water bottle (used after I was thirsty) [covers outtake tube to prevent clogs]
(9) hydroton (10L for $22 on Amazon ... way too much, but good to have) [growing media]
(10) outlet plug timer (had laying around)
(11) air pump (~$5)
(12) bubbler and tubing (left over from past projects, but probably only a few $)
(13) small plastic plant containers (3-inch slotted mesh pot ... still could go smaller, Amazon set of 25 for $8.85)
(14) aquarium sealant
(15) Goldfish and fish food
(16) Optional: gravel, tank art, fish tank plants, your *plants (I started with basil, rosemary, and an ivy plant).

*plants are necessary for the system, but what plants you use are up to you.

Step 2: Prepare the Media Tank

The tank that holds the plants [media tank let's call it] consists of a number of parts:

(1) The intake pipe where the water is pumped in from the fish tank (exits above water line);
(2) The outtake pipe (the top is where your waterline tops out, but has holes throughout for full draining); and
(3) The media and plants.

First, I filed down the legs of the smaller tank so that it fit comfortably on top of the fish tank.

Then I addressed intake and outtake holes, to which you need 2 holes in the bottom of your plastic container. I took my 1" PVC (intake) and my 1" coupler (outtake) and traced an outline of each on the plastic bottom and then used a very small drill bit initially, very carefully (so as not to create any cracks) and then a file to round the edges.

For the intake, I glued in 1" PVC pipe that held within it 1/2" rubber tubing from the water pump, that I then coupled with a 1/2" to 1" converter corner piece that connected to a 1" corner PVC piece (I wanted the water to end up going downwards to avoid any splash).

For the outtake, I glued in a 1" PVC coupler and then screwed in to the top 1" PVC pipe and a 1" corner to the bottom. The outtake piece I then drilled holes throughout from top to bottom (within the media tank) with a very small drill bit, so as small levels of drainage could happen continuously, and then when the pump is off, full water drainage of the media tank is possible. The top of the outtake 1" PVC pipe is left open and it is the main source of drainage when the pump is on.

The water bottle (I used a Poland Spring or the like), you cut the top 1/3rd off (whatever gives you a height just greater than your 1" outtake PVC pipe, and then you cut slits in the sides to allow water in but still small enough to prevent hydroton from being next to the outtake PVC pipe (constant flow requires your outtake to actually pull water out of the system, having hydroton and/or plant roots touching your outtake tube directly could cause blockage .. and then unpleasant water splashed all over your floor.). You can use pretty much anything to protect your outtake pipe.

To seal each, I used aquarium sealant (make sure to get aquarium specific sealant as it is waterproof and fish safe).

NB: The elbow 1/2" to 1" converter shown in the picture ended up being used in the intake section connecting the tubing from the water pump to the corner that empties into the media tank.

Step 3: Prepare Fish Tank

Add gravel and whatever fish tank art desired, and locate a good position for the pump to reside under the media upper tank.

Connect the tubing within the intake PVC pipe to the water pump (make sure your water pump is graded to pump up how many ever inches/cm/feet/meters to your media tank).

Setup air pump, tubing, and bubbler (fish like aerated water)...this will run 24/7/365.

Fill tank with water.

Also, this would be a good time to setup your automatic feeder on the other end of the tank (depending on your pump strength, you do not want to clog the pump by it being so strong it pulls all new food down into its vents). I had to use a small piece of cork I had laying about to supplement the feeder's grip on the side of the tank.

Step 4: Test Your System

After you allow ample drying time for your aquarium sealant (I believe 48 hrs is suggested), test your system.

Plug in air pump ... does the bubbler function?

Plug in water pump ... how strong is the pump's flow? Most water pumps are adjustable, adjust the pump to the maximum strength possible that does not make any water splash (remember that with hydroton media in the upper system, splash will be further reduced).

Does the outtake flow function well? If it is too strong an outtake, you could use a 1/2" to 1/4" corner converter on the bottom instead to shorten the outflow ability.

Let the system run for a little while and test every aspect possible. It is better to take your time here and make sure things are all functioning smoothly now, rather than after you start adding live items to the system (trust me! Not that I did that. I have a friend, she lives in Canada, you wouldn't know her, she told me about it).

Once fully tested and any adjustments made, we are ready to go live!

Step 5: Add It All In!


After thoroughly washing your hydroton (it is clay and comes a little messy so a thorough rinse will help a lot, that is normal), add it to your media tank. Add enough to fill just below the line that your mesh plant holders will sit.

Fill your plant holders with hydroton and your plant (you want the main part of the roots to be just above the waterline so roots can grow downward but will not rot). Place your plant holders in the media tank and fill the rest of the hydroton in. You want your hydroton to top out just above the waterline so that the top level is not in the water (this will prevent excessive algae growth on the top surface of your hydroton).


Cycle your water (and treating it if you used tap water) ... do a quick Google search if you are new to fish and fish tanks--this pretty much prepares the tank to house fish without shocking their systems too much. It allows good items to flourish in the tank.

Add your fish (not too many to start as gold fish create a lot of waste and thus ammonia and you need to allow time for you plants to grow and root in your system).

Don't forget to set your automatic feeder (for young gold fish, feeding once a day around 10 AM is good, and as they get bigger, feeding a second time a day is recommended).

This would also be a good time to setup your timer. I used an old one I had that allows 15 min precision so I set it to be on 45 min out of every hour. During the 15 min it is off, the water drains from the media tank and allows for maximum aeration of the media for the plants. This helps grow, I believe, good bacteria that helps breakdown the waste in the water faster.

Step 6: Enjoy!

Test out different plants and name your fish cool names (I am a fan of the ironic "Jaws" for at least one gold fish). Our two algae eaters are named for the two eels from the Little Mermaid.

Now even little kids (or adults with kid hearts and love of creation) can enjoy aquaponics in the city!

These systems are so basic in principle that with an efficient assembly setup, they should be easy enough and inexpensive enough to make that anyone who wants one could build/own one. I'd love to one day to be able to create an efficient modular system that people could buy as a kit and use as an educational tool but in any space restricted environment. Add a grow light, if you can't place the system by a window and now it doesn't even need natural light! Plants are lacking in so many houses and dorm rooms, this could make it both fun and low maintenance.

Potential improvements: Larger grow container that straddles more of the fish tank; automatic feeder integrated into the system/smaller; decide if constant flow without draining is efficient enough to remove timer and would allow for no change in fish tank water level [though the long tank does allow for minimal water height change at present]; optional grow light attachment; removing hydroton media and using just water would allow for a lower grow container level.

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    25 Discussions


    3 years ago

    Plants have been growing great off the single gold fish (to be changed with a new, bigger home for him, I know). My pump from PonicsFarm (Amazon) just died so am upgrading to a 120 gallon pump over the 66 gallon punp I had. In the meantime, a temporary DWR setup is in place as I am taking this opportunity to revamp the grow tank-- going to see if a loop siphon or U-siphon could work better for the system, in that I would not have to have a timer that could have given the pump a little too much additional stress. Will also black out the sides facing the sun as well.

    I'd love to have some sort of constant flow system so the tank level doesn't change, but everything I've read says it is inferior for the plant growth and allows for possible buildup in the grow media without solution. Oh well. If anyway has advice, I think a loop siphon will at least make it more smooth than the timer.

    Also, thkights on snails for control of algae growth?

    I set up an aquaponic system in a greenhouse with an aquarium like
    yours. The first thing that we did was stabilize the temperature of the
    fish tank with blackout fabric. Once we had reduced the temperature
    changes to an acceptable level (2-3 degree swing from day to night) we
    chose a guppies, as they deal with temperature changes more readily than
    other fish and fit in our 78-80 degree F environment. During my
    experiment I noticed that the sun was the most challenging variable
    because it caused algae blooms in the clear tubing (which probably
    removed some of the nutrients in the water, not to mention the disrupted
    water quality of the fish) and the temperature swings required lots of
    trial and error to control. My suggestion to you would be to move the tank out of the sunlight
    and find away to keep the planter in the windowsill using solid colored
    tubing to move the water from fish tank to planter. Also get a solid
    colored plant bed instead of a clear one. Although if its been working alright so far, that's super! Nice instructable.


    4 years ago on Introduction

    From my experience, you will need more fish for fish waste and "fertilizer", or your plants will be underfed. Be sure to foliar spray your plant so it gets additional nutrients while you cycle your system.

    Also, do you plan to add red wigglers to the grow bed? Plants don't eat fish waste, they eat the broken down product and worms are the ones that make the nutrients readily available to your plant roots.

    1 reply
    Bree Rodrigueza206h

    Reply 4 years ago on Introduction

    Do you know of any literature that would provide me with a better
    understanding of fish waste conversion to plant available nutrients in
    aquaponic systems? The book 'Aquaponic Gardening: A Step-by-Step Guide to Raising Vegetables and Fish Together' by Sylvia Bernstein wrote that since fish are cold blooded their waste is already available in nutrient form to plants. I found this statement a bit suspect as it didn't explain why the reader would assume that cold blooded animals would produce such a waste. I would greatly appreciate any advice you could give me.

    The book also suggested adding red wigglers but I postulated that the writer was working off a large ebb and flow system which is better suited to provide spots where the worms won't 'drowned' during the periodic flooding.


    4 years ago on Introduction

    So an update .... we now have one gold fish (I know, it is too small a tank, we will change fish when we have a new home and the fish gets bigger), one small cory (I believe), and a snail. I have blocked sunlight from the side of the grow bed, and a little from the tank itself, but hoping that the snail will start getting hungry and cleaning the tank himself. I have also added a small filter at the present to make sure there is enough flow/cleanliness in the tank, as well as the bubbler I have had since the beginning.

    I now have rosemary, basil, thyme, and mint growing and all seem to be reacting VERY well to the nutrients and water flow of the system. I will have to cut each back soon and dry some of the herbs but new growth (none from seed) have come in well.

    Re: red wigglers, given the aquaponics nature, I don't know if that is wise--my understanding is they survive in dirt and all-water would drown them immediately. WIth aquaponics, the good bacteria cultivated in the grow medium (hydroton in this case) helps break down the waste and turn it into positive nutrients for the plants. The use of a timed flow system (rather than a continuous flow one) allows for better growth of that good bacteria.

    Again, this is my first system and I have learned from web site, videos, and Instructables comments on this project in order to improve thus far. So, a big thank you to everyone who has donated their advice!


    4 years ago on Introduction

    This is a creative use of space! I love it! You definitely have my vote. Great system!


    4 years ago

    i try to keep the tank above 66' C, but can definitely add a heater if that is a better situation. The temp will vary with the light, but we try to keep the apt from being too cold.

    And I definitely get the frustration, Pet Stores have yet to give great advice thus far. In the future I will do kore research online. I just assumed, incorrectly, that those whose job it is to sell a pet/animal would be an expert.

    To note, I had already added a bubbler (one of the long flexible tube versions) for constant aeration. I am thinking of adding a small filter to assure the water is properly primed for the fish though I do not know how the aquaponics setup affects it. The plants have started to root nicely. I also added a banana underwater plant (or that is what they called it in the store) for additional filtration and aeration purposes.

    I will also look into the cloud mountain minnows in general.


    4 years ago

    Interesting. I was going off the advice of the pet store I bought from which said 4 or 5 goldfish could fit in the tank and we decided on less. That said, upon further research, they gave horrible advice. It looks more like a betta fish would be a far superior choice. I'm not sure if I can edit the Instructable, but I will try. NB: This is an Instructable about an aquaponics system, not a keeping goldfish Instructable. I apologize for trusting the pet store too much, but railing against Instructables for featuring one that mentions goldfish is a bit excessive. I appreciate the education though! That is what this site does best!

    2 replies

    Reply 4 years ago on Introduction

    This happens a lot. Pet stores are more interested in selling fish. Over and over and over again...

    The only reason I got mad at instructables is because they've done this several times in the past and maybe I'm too tender hearted but if you're sending a newsletter out to thousands with wrong advice on how to take care of an animal that will only end in it suffering or dying, that's just not cool. Not trying to bring you down or anything.

    That being said, if you don't want to invest in a heater the next best inhabitant I could see for a smaller tank is white cloud mountain minnows, which can be kept in a small school. Here's a calculator you can use to plan out what you want to put in any size tank-


    Reply 4 years ago on Introduction

    Actually betta would be a poor choice too low bio load and it would only be the 1 fish.


    4 years ago

    Okay, so the somewhat unanswered question, from the fish-knowledgable community, is ... what fish would be best to populate this setup? Would love a few options! Thank you ahead of time!

    1 reply

    Reply 4 years ago on Introduction

    Hi there! Apologies for what will be a long post, If I may offer some observations/ suggestions? Your 'best fish for this setup' question is really dependent on what is your tank's temperature? With what I'm assuming is direct sunlight exposure your tank will heat up during day only to fall to your apt.'s temp at night. This temperature fluctuation, if extreme, will stress most fish and likely eventually kill them. As has already been noted, your goldfish are temperate fish, and the plecos are tropical, some-one's not going to be happy; )

    The other already-noted factor is the size of your setup. With all due respect to some of the other posters, the tank volume is not as crucial as many have been lead to believe, it's the WATER SURFACE AREA and water temperature that largely determine any tank's carrying capacity; ie: the larger the interface between water and air, the more O2 the water can absorb, and cooler water absorbs more O2 than warmer water. Agitation further increases O2 absorbsion and also drives off CO2.

    With that in mind, If you set up a spray bar at the top of the media tank and drilled a few dozen 1/8" holes in the bottom, (cut off your return tube to say an inch as an overflow and screen it, natch) you will increase your O2 absorbsion potential by both increasing the water surface interface flowing over the media, and agitating the fish tank surface. Putting the airstone in the bottom of the media tank will also add the water's O2 absorbsion potential AND insure air supply to the plant roots, which is vital in a hydro/aquaponic system.

    Now, just to clarify getting back to your fish tank size, too small a volume for the size of the adult, full-sized fish WILL stunt their growth as well as stress them.

    Overcrowding IS normal for commercial operations, and not every commercial operator compensates, (or knows how) but most compensation measures are beyond the scope or ability of the average hobbyist.

    As a 40 year fishkeeper with commercial breeding experience in all combinations of tropical and temperate freshwater and marine fish, plant, and invertebrate species, I DON'T RECOMMEND IT!

    Get back to us with your fish tank temperature range and we'll all be in a better position to recommend species for your set-up.

    Oh, and welcome the wonderful worlds of fishkeeping and aquaponics!


    4 years ago on Introduction

    It's will could be nice and easy to us, if you can show the series of step in pictures with minimum words.

    1 reply

    Reply 4 years ago on Introduction

    He did. At the top of the page, under the title and next to the download button, click on the square button with nine little squares in it. That will allow you to view all steps at once.

    Mr. E Meat

    4 years ago

    Nice! I would black out your grow bed to prevent algae growth though.

    2 replies
    Mr. E Meatagreenspan

    Reply 4 years ago on Introduction

    With the clear grow bed container, you will get algae growth on the sides (especially if you ever get direct sunlight on it). You've thought about algae growing on the top. Cover the the sides to stop it growing there too.

    Also, having fish myself, I have to agree with Trusthapo's assessment of your fish choice. You're probably fine for now though. If you're like me, you'll probably be wanting a larger tank soon anyways! Larger tanks are actually easier to take care of too!

    Good luck! Have fun!


    4 years ago on Introduction

    I really really reeeeeeally hope you're not going to keep 2 goldfish and 2 plecos in a 2.5 gal tank? Goldfish need at least 10 gal per fish to do well, and depending on the species of pleco you bought those could grow to a foot long each and plecos produce even more waste than a goldfish. These are NOT small aquarium fish!! If you absolutely need a pleco in there, go with a Bristlenose Pleco as those will stay only a couple inches long, but move those goldies into a 25-30gal tank! <3 *owns several large, fat goldfish and 2 bristlenose plecos

    1 reply

    Reply 4 years ago on Introduction

    Here here! Instructables as a website just doesn't seem to care much about keeping fish happy and healthy :\ I don't blame keepers for making beginner's mistakes but it's awful to me that a big site like this likes to regularly promote 'ibles that compromise the health of pets!

    I just hope more people wanting to do this 'ible see our comments before they set out to work. Anybody wanting to keep goldfish that needs advice should feel free to message me and I will be more than happy to help!