Backyard Aquaponics
A place to discuss aquaponics

Hello

I'm totally green at this stuff so please be gentle.

I just bought a 75 gallon fish tank and now wanted work on getting myself a grow bed. My system will be indoors in our living space. Based on the information provided me by the tilapia fingerling sellers I should be able to get 15-20 tilapia in that space.

So a few questions are:

• Based on what I've read I need something about about 75 gallons for the grow bed to get proper filtration. Is that about correct?
• Is there a sticky for grow bed ideas? I don't want it to be too much of an eyesore but I've seen IBC totes and poly feed liners used as grow beds. Standard grow beds aren't cheap at all for 75 gallons.
• Will the system create any odors?
• I've seen people say 15-20 is too many for 75 gallons and others saying density actually relieves pressure and the fish from getting territorial. Anyone have any experience with this?

Thanks!!!

A healthy balanced AP system shouldn't create any unpleasant odours.

A 1:1 ratio of water to wet gravel is good.

A systems safe fish stocking capacity is primarily determined by the amount of bio-filtration (ie: wet gravel) in the system. If you then provide a 1:1 gravel to water ratio, the fish to water ratio will be sorted.

A wet gravel to water ratio anywhere between 1:1 and 0.5:1 works well for backyard sized systems.

Tilapia are a fast growing fish, as such you should ideally have around 25L (6.6 gal) of bio-filtration (wet gravel) per fish to get them safely through to plate size.

So if your GB has a maximum gravel capacity of 280L (75 gal) and you have the recommended 50mm (2") dry layer at the top of the gravel, depending on the GB shape and gravel depth you most likely have around 230L (60 gal) of wet gravel providing bio-filtration. This would safely maintain 9 Tilapia through to plate size IMO, 10 at a stretch.

Nice. Thanks for the reply.

Anyone have any advice on where to get a reasonably priced grow bed?

Depends on your definition of reasonable. Look on Letgo, Offerup, Craig's list. No telling what you might find to use for the growbed. Sometimes a hot tub is free if you pick it up. Cut the center out, build something attractive around the part you intend to use and trssh the rest. Concrete mixing tubs from a home improvement store. Not very deep, but depending on what you want to grow, it can work. Use your imagination.

For an indoor system I'd look at heavy duty totes, or build wood beds and line them. I used some smaller totes to provide a bit of extra filtration for my tilapia tanks indoors for a while using hydroton so it doesn't weigh as much as gravel. Not sure if the totes would have held up against the weight of gravel.

Out of curiosity will a clear aquarium be a haven for algae? Is there anything I need other than a pump and air stone to keep the fish happy?

Fish food will help