CichlidFish.com - Fish That Think.

how big of a tank would i need for two 7" oscars and and algae eater?

For comfort, 70 or bigger. You need larger tanks for a couple of reasons. One physical territory, 2 water volume, three swimming space, ie the tank footprint. If you are limmited on the size of a tank, get one that has a larger footprint over water volume. It is more important for the fish to be able to swim and turn in the tank, than it is for the fish to rish or fall vertically in a tank.

I would think 90 gallons should be a good size, if it was just the 2 oscars a 75 gallon would be fine and it still possibly could be. But if you wanted to be sure about your decision I would say 90 gallons or maybe a little bigger would be best.