The only concern that begins to occur in my mind when trying to construct the volume of an aquarium prior to its materialisation is the matter of territorial requirements.
From the perspective of a living organism that lives by itself or in the company of its better-halves or be it in a dense colony, any other species in 'its proximity' will appear as a threat to its existence and consequently stays on the look out singly or collectively and carries out operations or actions in ways that it is bestowed with consisting of aggression of varying degrees.
With the aforesaid in mind the minimal expanse of personal space must be arranged for by way of affording at least 2' to 3' foot of width coupled with the necessity for elongation that should depend on the number of animals, species as well as their associated demeanour. Height is that headroom that are liked by many who try to seek safety through escape or utilised as grow-room. Depth from all angles must be taken into account.
It is worthwhile to give it a thought regarding the preference of humans who would love to not let go any opportunity of living in a spacious dwelling or a vast expanse of open space or both. Though, like the clowns, we have exceptions amidst us too.
It should all be laid out through a meditative approach fused with passion. Use the sciences along with human compassion. Every organism possesses a psyche and everything that goes with it.
Also, lavish your pets as far as you can afford. They are a responsibility and you are no proprietor of a circus here.