I forget where to find it but out there somewhere in the great internet there is a formula to calculate the approximate o2 requirements and related waste of fish by size. Of course it requires a fair bit of math, but could be useful for the budget minded aquarium hobbyist trying to raise a rather large fish. I've seen people stuff poor arrowanas into 6 foot long tanks, but it just looks so sad. Like fish Jail. So did you have any ideas of fish you had in mind?