Stocking Levels

[Jamie24]

I've read many times from many places that as rule of thumb it's 1 inch of fish per gallon but what about this surface area argument I've also been hearing ?? Let's take into account the Aqua One tanks, the Aqua one 620 holds 90 litres, 20 gallons so 20 inch of fish however the 620T holds 130 litres, 29 gallons so 29 inch of fish but the surface area of both tanks are the same so what should be taken into consideration more ???

Should the different levels of fish area be taken into account also, for example plecs and clown loaches which are prominently bottom feeders should they be classed in the same surface area of hatchet fish are top level fish ??

 

[Gvilleguy]

Well,in my somewhat limited experience with my own year+ old tank (and being a regular forum reader), I have found the 1-inch-of-fish-per-gallon rule a good place to start, especially with a new tank. But, technically, surface area, and therefore the oxygen exchange capacity, is the real fact you need to deal with in the long run. It is how much oxygen exchange you can get at the top of the tank that matters the most.

The 1-inch-of-fish-per-gallon rule and the 1-inch-of-fish-per-12-sq-inches-surface-area rule should both be considered in your calculations. Why not calculate both ways and choose a position in between the two? I think you will find them to be close to the same value, anyway.

Other factors to consider:
1. Make sure your calculations are based on the average ADULT size of the fish being considered.
2. Oddly shaped aquariums that are tall/narrow: put more weight on the surface area calculation.
3. Regular rectangular shaped aquariums that are not tall: 1-inch-per-gallon rule is probably fine.
4. If you plan to stock wide-bodied / fat fish, your stock plan should be more conservative. I have seen a figure of 1 inch of adult fish per 20 square inches of surface area in that case. But I would search the internet for a wider range of figures on that.
5. The maturity of your filtration (bacteria colonies) is also very critical. I feel that a tank less than 12 months old should have a more conservative stocking level, since the filter will be more prone to fluctuations and less quick to recover from problems. A fully-stocked tank with a mature filter is going to be more stable than a 6 month old filter trying to handle a full stock.

To answer your other question -- the level of where the fish "lives" in the tank does not matter - it's all about getting oxygen exchanged at the surface.

 

[fluttermoth]

Also, don't forget that all those 'inch/cm per gallon/litre/square inch' rules apply only to the average, small, slim bodied tropical fish; they are useless for any fish that grows to over two or three inches, cold water or marines.

 

[DavidAl]

Ditto all of the above.

Stocking levels should be based on many factors. The one inch per gallon rule, as fluttermoth mentioned, should only apply to small, slim-bodied fish, preferably under two inches as adults. You can get away with putting ten 1-inch fish in a 10-gallon tank, but a 10-inch fish would never survive in a 10-gallon tank.

Factors to consider, in addition to what gvilleguy mentioned, are: temperament, swimming levels, water parameters requirements, compatibility, breeding customs, diet, territorial needs, maintenance requirements, etc...


David