Which Gallons To Use When Choosing Number Of Fish?

[Charlie06]

Ok, I know how you are supposed to have 1 inch of fish per 1 gallon (I think that's right), but which gallons? There are UK and US gallons so which to use to make sure you have the correct number of fish? Our tank is approx 24 UK gallons or approx 29 US gallons, that's a big difference. Which do I go by?

Which way have you guys done it please?

Charlie

 

[nmonks]

Don't use either. Volume is NOT a reliable measurement for estimating how many fishes can be put in a tank. It is much better to use surface area. Allow about 10 square inches per inches of small (guppy/platy) sized fish.

For example:

1. A tank 24 inches long by 12 inches wide by 12 inches deep.
2. Surface area = 24 x 12 = 288 square inches.
3. Divided by 10 = 28.8 = 28.8 inches of small fish.

Why? What restricts capacity is (among other things) the rate at which oxygen gets into a tank. Imagine a 10 gallon tank. One very tall and thin, and the other low and flat. The tall thin one can hold a fraction of the fishes that the low flat one can because it has less surface area for oxygen to get into the water. Same volume but different numbers of fish.

Incidentally, this is why bubbles and water turbulence help in aquaria. They don't "push" oxygen into the water, but what they do is make the surface area bigger (because it's undulating instead of flat). More surface area = more oxygen.

If you want to do the math a quick way, I have a little program called Fish Tank Tool that comes with pre-set aquaria as well as boxes for typing in the height, width, and depth manually. It will calculate stocking amounts for you instantly. It comes in Mac and Windows flavours, and is free.

Cheers,

Neale

 

[Charlie06]

Superb, thank you for the information.