Drained down my tank, plucked out all the fish, stretched them out nose to tail ....... 345.5678 inches of fish in 356.789 net gallons of display water after measuring actual displacement. So I'm at slightly below an inch of fish per gallon. I then applied a 'girth' factor (a fatter 4" fish has a higher contribution than a skinny one) of 3*pie to get 1.5 inches per gallon. OK, now what .....?