Fish tank aquaponics system growing basil

Fish Tank Aquaponics System

DIY Home Aquaponics With Off The Shelf Parts

From 2012 to 2016, students and I designed, built, and ran an aquaponics system at Jasper Place High School. While the system worked well, and we learned a lot, it would be too cumbersome and expensive for the average home. So I started wondering, if I were to take everything I’ve learned, how would I approach an at-home aquaponics system? My goal is to create an elegant, home aquaponics system from a standard fish tank and off-the-shelf parts for as little money as possible. Here’s how I build my fish tank aquaponics system.

Fish Tank Aquaponics Design Criteria

Before designing my fish tank top aquaponics system, I created a list of criteria necessary for success.

Simple and Elegant Design

A DIY home aquaponics system needs to be as accessible as possible. The system I built at the school had a few fussy components, primarily the bell siphon, that took weeks to get right. An at-home aquaponics system should be straightforward and beautiful. Yes, I want something functional, but I’d like something I’m not ashamed to display.

Foolproof

The last thing anyone needs is dead fish, plants, and a flood. Good design is redundant, safe, and reliable. The wise aquaponics builder will ask, “what happens if the power goes out? Will the system implode and make a mess, or will everything survive?”

Affordable

A DIY approach should be affordable and repairable. Replacement parts should be easy to find and simple to use. For this reason, I’ve also decided to build the system with standard fish tanks – the kind you can track down on Kijiji, Craigslist, or Bunz for dirt cheap or free.

Modular and Customizable

You should be able to start small but expand your system to meet your needs and capacity. Our fish tank aquaponics system should be flexible enough to adapt to fit our desired scale.

Accessible

What use is a home aquaponics system if it requires a master carpenter to build and a science degree to maintain? Our fish tank aquaponics systems ought to be simple enough for a novice to build and easy to service.

DIY Fish Tank Aquaponics System Design and Build

At its core, an aquaponics system has two components; a fish tank and a grow bed. The fish live in the tank and are cared for in much the same way they’re cared for in a conventional take. However, instead of a conventional filter, water is circulated into a grow bed where beneficial bacteria convert fish waste into products accessible to plants. Water returns to the fish cleaner than when it left, and the cycle repeats.

Fish tank aquaponics system growing basil
Fish Tank Aquaponics System Growing Basil

The Fish Tank Aquaponics Setup

I inherited a 40-gallon fish tank and some fish, so I used it as my base. I left the tank unaltered but replaced the conventional water filter with the growing bed and medium. A small pump on a timer will cycle water from the fish tank to the grow bed on top, and we’ll let gravity return the water to the fish.

The nice thing about this design is that we don’t need to modify the fish tank. The only thing we need to do is build a grow bed and plumb everything together.

The Aquaponics Grow Bed and Filter

The grow bed is designed to rest on top and replaces the existing fish tank filtration system. Bacteria in the grow box convert the toxic ammonia in fish waste into nitrate that the plants can access. In addition to growing food, the grow doubles as a biofilter.

A grow bed can be as simple as a food-grade plastic container, but I have a lot of 1×8 pine from building beehives. While wood looks nice, it doesn’t hold up to water and requires a liner. In hindsight, cladding a plastic container may have been easier. In the end, I lined my wooden box with coroplast and some pond liner that I picked up in the seasonal section of the hardware store. I’m happy to say that the grow bed’s inner liner and wooden outer have held up exceptionally well over the years.

Aquaponics grow bed with coroplast and pond liner
Aquaponics Grow Bed with Coroplast and Pond Liner

Aquaponics Growing Medium

Without creating mud, you can’t use soil in an aquaponics or hydroponics system. What we need is something that drains well and has lots of surface area for ammonia-digesting bacteria to grow. Gravel works but is extremely heavy, so I opted for more expensive but highly effective expanded clay pellets. Lightweight expanded clay pellets (LECA) can be found online or at most garden centres. Leca is ideal for aquaponics because it doesn’t break down and has a very high surface area where bacteria can colonize.

Aquaponics Plumbing

There are a few approaches when it comes to plumbing an aquaponics system. The key to any method is establishing a healthy mixture of water, nutrients, and oxygen to the plant roots in the grow bed. Too much water and the plants drown – too little, and they’ll dry up. I’ve found that a good mixture involves flooding the grow bed for 15 minutes every hour. We can achieve this through bell or U-siphons that automatically cycles water through the beds at regular intervals, but they can be complicated to build and hard to “tune” to the right balance of water and oxygen. To keep things simple, I opted to plug a small submersible pump into a $10 timer set to turn on once an hour for 15 minutes – done. Simple.

Lighting The Aquaponics System

The use of supplemental lighting depends on the location of your system. Mine’s inconveniently tucked away in my basement, so natural light isn’t an option. I opted for two T5 lights that I will later upgrade with LED replacement bulbs.

The obvious solution would be to pull the system out of the basement and into direct sunlight.

Maintenance and Growing Food

The system requires minimal upkeep outside of daily feeding and care of the fish. I’m pleased I went with a timer to regulate water cycling as the plants seem to love it, and I don’t have to fiddle with finetuning a bell siphon.

Adding plants is simple. I picked up some basil from my local grocery store and divided it into small plugs. They took quickly and provided a hefty handful of fresh leaves at least once a week – I haven’t bought any basil since turning the system on. I think your best candidates and bang for your buck are leafy herbs. Leafy greens are easy to grow in an aquaponic system, and herbs are more expensive at the grocery store.