Standard for minimum tank size for fish...thoughts?

[LordJoshaeus]

Hi everyone! I am developing a personal standard for estimating the minimum tank size a fish requires...how does this formula sound?

Possible standard for fish tank minimum size;
- Do not keep any fish in a tank smaller than a 5 gallon, except for quarantine or
breeding purposes (for small species)
- Find the maximum standard length a fish is likely to reach (often 80% of the
figure on fishbase) and divide the length of the narrow end of the tank by that
value. The narrow end of the tank should be 2 times that 80% value, or else
the tank is not suitable for the fish.
- Tank height must be at least twice that of the height of the fish.
- Add the length and the width of the aquarium together, and then divide this
by the above 80% value. If the result is less than 8, the tank is not large
enough. Active swimmers or aggressive species need 12 or more; if both active AND
aggressive, go to 16. Almost all saltwater fishes are going to be aggressive
and/or active, so this value must be 12-16+ for these.
- Tank size must also accommodate the fish's temperament (aggressive animals need
larger quarters), the bioload, and other considerations. If a fish consistently
does badly at a certain tank size, go larger.

Thank you for your thoughts on this

 

[Bleigh]

Seems interesting. I imagine you played around with some actual dimensions while thinking through this. If so, would you mind sharing them?

 

[Brew12]

Hi everyone! I am developing a personal standard for estimating the minimum tank size a fish requires...how does this formula sound?

Possible standard for fish tank minimum size;
- Do not keep any fish in a tank smaller than a 5 gallon, except for quarantine or
breeding purposes (for small species)
- Find the maximum standard length a fish is likely to reach (often 80% of the
figure on fishbase) and divide the length of the narrow end of the tank by that
value. The narrow end of the tank should be 2 times that 80% value, or else
the tank is not suitable for the fish.
- Tank height must be at least twice that of the height of the fish.
- Add the length and the width of the aquarium together, and then divide this
by the above 80% value. If the result is less than 8, the tank is not large
enough. Active swimmers or aggressive species need 12 or more; if both active AND
aggressive, go to 16. Almost all saltwater fishes are going to be aggressive
and/or active, so this value must be 12-16+ for these.
- Tank size must also accommodate the fish's temperament (aggressive animals need
larger quarters), the bioload, and other considerations. If a fish consistently
does badly at a certain tank size, go larger.

Thank you for your thoughts on this

Love the concept, hopefully I'll have time to pick some fish and run the numbers to see how it works in practice.

The only thing it won't account for is the aquascape in the tank. I feel that for a fish to be appropriately housed in a system it must have enough structure to feel safe and enough space to swim. I've seen some 180g tanks so full of rock and coral that I wouldn't put a tang in it. Hard to quantify that with math.

 

[LordJoshaeus]

Seems interesting. I imagine you played around with some actual dimensions while thinking through this. If so, would you mind sharing them?

Sure! I used a royal gramma and a sohal tang as tests for this. I'll start with the grammas.

Royal grammas hit about 8 cm in length (I used centimeters with the gramma because it gives me more precision, but for reference that is just over 3 inches) and assumed that I would want the length plus the width to be 12 times that of the gramma (since they are neither hyperactive nor outrageously aggressive...unless you try to put two males in one tank, that is, in which case a public aquarium might not be big enough to keep them from killing each other). From my calculations, the smallest common tank size whose length plus width is more than 12 times the length of a royal gramma is a 20 long, which should be large enough for a singleton and is probably also large enough for a pair.

Sohal tangs are more complicated, as their large size means that the tank width becomes important AND they are both active and psychotic (they would definitely need a length plus width value of 16+). 14 inches is about the size a sohal tang usually reaches in aquariums (fishbase lists the recordholder at 40 cm, or around 16 inches), so a sohal would need a tank 28 inches wide; a tank 28 inches wide would need to be 196 inches long (14 times the length of the tang) by this standard to house sohals (or, more likely, a single sohal) comfortably. This falls quite comfortably into common ranges for tank sizes for sohals, though even at that tank size sohals are such vicious tankmates that they could still decide to murder their neighbors in such a setup...basically, sohals (or tangs in general, for that matter) require too much space for most of us to keep them appropriately.

Love the concept, hopefully I'll have time to pick some fish and run the numbers to see how it works in practice.

The only thing it won't account for is the aquascape in the tank. I feel that for a fish to be appropriately housed in a system it must have enough structure to feel safe and enough space to swim. I've seen some 180g tanks so full of rock and coral that I wouldn't put a tang in it. Hard to quantify that with math.

Very true! This was not taking hardscape into account. Like all such formulas for tank size, this one isn't perfect...however, I am pretty confident in this one, as I generally get reasonable stocking results when I plug fish into it.

EDIT; Here is a crude, to scale sketch of a sohal tang in a tank that length (I assumed it was 30 inches high);