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.]

Materials:
(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!

MEDIA TANK

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).

FISH TANK

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.