I think you can have too big a tank. A small animal in a large tank tends to get lost, though you can do it. Tank size is an interesting idea with cephs because they so radically change size through their lives. I prefer a small tank when the animals are young so I can make sure they are eating and to be able to do health checks. Besides that, it def varies by species.
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Please forgive the line by line, but it feels important to address all these. If I am missing something please let me know.
Cuddlycuttlefsh;184145 said:
A recommendation, Square tanks are the way to go,
they allow more gas exchange on the surface
Surface area is surface area regardless of shape. Also gas exchange is mostly a function of breaking the surface tension which seems to have no relation to shape.
more room for beneficial bacteria
Again, surface area is surface area, but more importantly, room for beneficial bacteria has much more to do with the substrate provided for those bacteria rather than the shape of the container.
more room for tank inhabitants
I am not sure how square equals more room. 100 gallons is 100 gallons (excluding extreme shapes).
much easier to siphon the tank because the water level isn't too high
Unless the tank is a cube. Most commercially available tanks are not 'too high', and most of them are rectangular.
doesn't make the inhabits feel squash
Depends on the animal, and the argument can me made that a longer tank give the animal more space to stretch out and swim (its why most swimming pools are longer in one direction). I am also not sure how we can measure how the animals feel.
metel halide bulbs are not required because it doesn't have to have it's light to penetrate the water from a depth
I am not sure how the shape of the tank has anything to do with light penetration - its more the depth of the water which seems to have little to do with shape. More importantly, it depends on the animals in the tank. If you are doing just cephs, MH lamps are not needed regardless of the depth of the tank.
Square tanks are fine, but they seem to be more of an aesthetic choice rather than a husbandry choice.