[tophat665]

And they have been known to ram the sides of tanks and break them. When you get into the 300 gallon range, you're talking extra thick tempered glass which may, possibly, and I ain't going to be the one testing this and winding up with 300 gallons of water on my livingroom floor, prevent this.

Frankly, I think you're both right - 75 gallons per pacu sounds reasonable, but 300 gallons sounds like a good minimum size tank.