The Scientifish Process: Goldfish and Grow Beds

I’m no good at houseplants. All that required sunlight casts an awful glare on the television, and that’s not a sacrifice I’m willing to make. In fact, in an effort to impress Arrie the first time she came to my place, I bought $50 worth of potted plants (I removed the price tags) and strategically placed them around my house. Six months later, the ruse seems to’ve worked.

But I do okay with fish. Well, goldfish anyway.

For years, I’ve been interested in aquaponics, the marriage of hydroponics and fish tanks. I’ve had a system similar to this for about three years now. What follows is my third version of this setup. Again, this isn’t really a how-to, just a description of how we’ve done it. I’ll try to answer any questions in the comments, but I’m certainly no expert.

Fish Tank, Grow Bed and Light

There are two parts to an aquaponic setup: the fish and the plants. Our tank is fairly straightforward – a thirty gallon tank, undergravel filter, a three-stage filter, heater, aerators, fake plants, a Buddha statue, and the scientifish (who used the scientifish process, obviously).

A brief aside: The aquaponic setup is basically a (not very) grown-up science fair project. Couple that with the fact that I’m a huge nerd, and you get fish named Oppenheimer, Hubble, Leakey, Watson and Crick. (Coincidentally, there was a third cory cat named Rosalind, but she didn’t make it. Watson and Crick have been taking all the credit for tank cleaning ever since.) Arrie’s note: His smarty-pants fish are ruthless killers, by the way. I added Neruda and Bukowski to the tank in September, and they’ve both been murdered since. No love for the poets.

The science of it all is fairly simple. Fish poop. It’s pretty much all they do besides eat and explore the Eight-fold Path.

Oppenheimer and Leakey contemplating their navels

Resident bacteria convert that fish waste into nitrates (plant food). So all you have to do is move the water from the tank to a growbed, and you’ve got a hydroponic system.

It's a little sparse right now because we had to pull out the plants that didn't make the move well.

The hydroponic growbed is not much more complicated. The bed itself is a plastic tub filled with Hydroton expanded clay balls. It is fitted with a drain on each side (like these), with the left drain is raised about an inch. The right drain is the inlet and is connected to a fountain pump that draws from the undergravel filter. The left drain just gravity feeds back into the fish tank. Because the left drain is raised, when the pump is running, the water fills the tub an inch or two before it starts draining back out. The bed itself is sitting on a shelf about 8 inches above the tank to allow access for feeding, filter maintenance, etc.

From left: Serrano pepper, green onions, watercress, and basil cuttings

I made the grow light and hood from a concrete tube form cut in half and spray painted. The bulb itself is a fluorescent grow light I bought.

Everything is controlled by simple timers. The light switches on around 7 and turns off around 10. The pump runs for half an hour every two hours from 7 to 9. Everything in the fish tank runs all the time.

As long as you remember to feed the fish, everything else takes care of itself. The fish feed the plants and the plants filter the water.

It is *really* hard to take a picture of fish.

We’ve had prolific success with basil, some success with tarragon, crazy success with green onions, and a decent experience with a serrano pepper.

It’s not an overly cheap project (probably $100 – $150 total), but it’s really rewarding to make pesto from basil that your pet fish grew.


One response to “The Scientifish Process: Goldfish and Grow Beds

  1. Very interesting stuff! Thanks for sharing.

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