Re: Fish Stocking Calculators

Afternoon everyone!

I've always used the community creator on this website to calculate stocking levels for my tank.
However, I was nosying around the web today and came across Aqadvisor. I decided to give it a go and was a bit surprised to see that the percentage levels of stocking for my tank (this is actual stock plus a few attempts at adding fish that I like in order to see what the stocking levels would be like for different community scenarios) are much higher on Aqadvisor than they are here. Just typing in a random selection of fish gave me 63% on Aqadvisor compared to 43% here.

I'm very happy to continue using this site to guide my stocking level plans for my tank (especially as the community creator is much more generous than Aqadvisor), but I was wondering why they are so different – 20% could add up to a fair few fish! Obviously, I want to have happy and healthy fish, but was just wondering if anyone could tell me why the 2 sites are so different.

Thanks Sue,

No, I couldn't find any information on formulae used to calculate stocking levels. Also, it doesn't indicate what levels are acceptable, unlike the traffic light system on the CC.

When you say that the CC has been criticised for being over-generous, is that a criticism you'd accept as being true, or do you think the CC is safe enough to use as a guide providing you stay within the green or amber zones?

Great, that's just the advice I needed! Once again, thanks for your expertise!

The CC does actually state

An 'oversized' filter means one which is rated for at least twice the tank's volume, such as a 200 litre filter in a 100 litre tank

If your filter is rated for 50% more than the tank rather than 100%, maybe you should halve the extra of oversized compared to standard?

The filter in my main tank is rated for 240 litres. When it was in my old 125 litre, I did class that as oversized even if it wasn't quite. The same filter is now in my 180 litre which is only 25% over so I have to use standard internal now.

According to that article, the oldest guideline was based on a number of fish for a given surface area. The rule was devised before filters were used and the oxygen level of the water in the tank was limited to the gas exchange at the stationary surface. The surface area guideline was really an oxygen content of the water guideline. And according to the article, the 1 inch per gallon came about after confusing the 1 inch per 12 square inches, and 1 inch per gall of cold water fish. The article claims that it should be 2 inches of tropical fish per gall.


The diehard believers of 1 inch per gall also fail to quote the guideline fully. It should read
"one inch of cylindrical fish that grow no larger than 3 inches per gallon"
The 'rule' never has applied to fish longer than 3 inches or to anything but torpedo shaped fish. But that doesn't stop them using the guideline for angelfish and discus!

In my opinion, the main use of calculators is to stop newcomers going mad and overstocking. A newcomer should stick to the 'green' limit of the CC for several months. Once they get a better feel for the behaviour of their fish and how to monitor the tank, it is safe for them to exceed this.

I've just entered those fish (3 black phantoms, 9 glowlights, 1 oto and substituting 4 panda cories for the 2 peppered) and that comes to 94% with standard internal filter or 79% with oversized 

If you were to part-ex the cories for 3 more otos and 3 more phantoms that would give you just over 100% for standard internal or 89% for oversized. If one of the filters is rated for up to 100 litre tanks, that alone does make the filtration almost oversized (oversized = rated for a tank double the volume).
The reason I suggest rehoming the cories is that peppered are quite big fish and would do better in a bigger tank, and they need to be in a shoal but you don't have room for any more. It would also allow you the extra phantoms.