Quantifying "swim Space" Needed

[ldsdbomber]

I have been interested in the threads on stocking, and while it must involve a host of factors, in the first order, it can surely be summarised in terms of

bioload
which I am sure can be quantified somewhat by calculation of nitrogenous products from food and plant decay, fish waste and metabolism etc etc, and balanced against bacterial colony sizes and plants for processing that

but also
"swim space" or just "room"

How would you go about that. Since these fish generally live in rivers, their natural habitat is in essence an extremely long tank, implying that any home aquarium in effect is cramping the fish. But how do we even define cramping. An 8" fish in a 12" tank is "obviously" cramped, but is a 2" fish in the same tank? Is it defined by their perception of how much space is around them, can they sense/measure this in any way? Is it related to memory of some kind, so you can define the memory recall time multiplied by average velocity. Is it amount of room before they need to turn round. What if its a cylinder or round tank and no turns are required. Does a path round the circumference of a cylinder tank equate to the same "crampedness" as the equivalent horizontal area in a square requring a succession of 90 degree turns.

Has anyone ever looked at this or even made a stab at it?

 

[OohFeeshy]

There are guidelines for 'space' for large fish- the usual one cited is the width of the tank should be at least 1.5x the length of the fish, and the length of the tank should be at least 4 or 5 times the fish length. The length element especially varies a lot between sources.

I'd break down the space aspect further to consider it more, for example other factors could include

-Fish body type- 'bendy' fish like eels and arrowanas can turn in smaller spaces than an equivalently sized cichlid, for example

-Fish 'speed'- a fast moving fish like a bala shark needs comparatively more room than something like a large catfish that is essentially not moving for most of the time

-Fish sociability- you need to factor in a greater tank size if more than one individual is kept

 

[OldMan47]

There is no scientific way to define swimming space that I am aware of, but I can say that when I observe fish, it is a given that a fish that uses a fraction of a second to swim the length of his tank, is a fish that really doesn't have enough 'room' in his tank. That fish is one that would make good use of more space than he has and would probably respond well to a larger tank. I wish I could help more but that is the best that I can do and, unfortunately, it means that you need to go beyond where you should be to find that level of stocking in our tank. Where this leaves you is in the no-man's-and of trying to guess how new fish will respond to a new stocking level.