tank size

[David R]

here's my opinion:
ideally....

width: 1x the length of the fish (at least)
length: 3x the length of the fish (at least)
depth: 5x the depth of the fish (at least) - this is a guesstimate...use your judgement
I would at least make the depth the same dimension as the width.

Perhaps we need a sticky on arowanas and tank sizes, based on a realistic size you can expect them to grow to if housed and fed well, say roughly 2' for jar/asian, 30" for silver, probably 24" for black (maybe more?), and african? Yeah they probably can get bigger, and yeah some might stay smaller, but something roughly around those measurements would be a good average to work on. So based on that you'd want around 6x2x2' for a jar/asian/black, and around 8x30x24 for a silver. Those sizes may not be enough for some fish "for life", but you would certainly have around 3-5 years before the fish outgrew those sized tanks.