My Formula For determining stock for a tank

i came up with this formula today at school tell me what you guys think...

1 fish per 10 gallons of water plus one.

example:
10g- 2 fish
20g- 3 fish
30g- 4 fish

no fish exceeding one inch per gallon plus one.

example:
10g- no fish over 1-2''
20g; no fish over 2-3''
30g- 3-4''

I'm finding that this only works with tanks around 55g and down. what do you guys think? i know its hard to put a specific number on this but i find its a good rule of thumb.

**this is assuming all of the fish can coexist with each other, go in your size tank and you have adequate filtration.**

 

Thats a hard rule to establish. some would say 4 inch wrasses shouldnt go in a 30g etc...

Just understand adult sizes of fish. Some think putting a juvenile in a small tank is okay because it has not reached its full size. But a 1 inch blue tang and a 8 inch blue tang both need the 8-10ft tank to grow in happily. Same goes for smaller fish like wrasses and others.

because of small lengths and sizes of smaller tanks set rules of size compared to tank cant exist. As you said "adequate filtration" i would say this would vastly differ among aquarists between being true and majority feeling their systems can handle heavy bio loads. Bio loads is where i feel stocking comes into play. How much live rock do you have will determine how much waste can be broken down so the more LR. the more fish your tank can handle. Protein skimmer, canister, hob, and other devices will assist in cleaning the water. But in terms of stocking i think bioload weighs in heavy on your LR for bacterial colonies to develope, and more places for fish to hide.. And every one's individual filtration compared to its lr and sand will determine their bioload capacity for their tank.

In terms of fish lengths for tanks, Just try to be as realistic as possible. For a 36" tank, the most that would be able to grow to adult hood and live comfortably would be a fish of only 2-3 inches in size. If your tank is 36" it probably shouldn't have a large active swimming fish in it like a tang.

For me i consider
Nano tanks up to 25g are up to 24" usually
small tanks 30-75g 24-48" in length
med tank 90g-120g - start at 48" but stay relatively small in width
Large tanks 125g- 180g this is where length and width increase to accommodate large fish like tangs.
Beasts- 200g+ can handle most fish.*(Queen triggers and sharks and large angels should stay int he ocean IMO)* I saw a 16" emperor angel in the store the other week. the tank was 8 feet long by 3 feet wide and it seemed tiny for this fish.

 

I would add that most often the limiting factor in stocking tanks is the O2 dissolved in the water. You can have have more fish in a FW tank compared to the same size SW tank because the often cooler fresh water can hold more O2 than the water in out SW tanks. If you are determined, it is certainly possible to handle excess waste with large filtration frequent water changes. The one thing you can't control is the amount O2 that the water can hold. Simply adding an airstone won't work because there is a point where the water becomes saturated and can't hold any more O2. Think of it like moisture in the atmosphere. Warm air can hold more moisture than cooler air. As warm air containing say 80% humidity cools, and as it does, the relative humidity rises, and we get rain.

I hope that helped and didn't just muddy the waters more lol.

Jake

 

Very true about the co2.

 

Don't forget to take into consideration the fish's swimming habits. A very active fish that likes to swim a lot will need at least a longer tank no matter what size the fish is or grows to.