Unless you have an over abundance of
LR, it will not really detract from available fish space. The only constradiction would be if housing large fish that need a fair amount of manuvering room like Volatians. If anything, the
LR will actaully help support the fish load better than just an
FO.
The general rule of thumb is 1" of fish for every 5
gal of tank less the tail. There is a <<
calculator>> on the forum that may help in future. For a 75
gal you are looking at about 15" of "tailess" fish...
This is not a hard and fast rule. It will also depend on the species. Whether they be benthic, aggressive, heavy waste producers or over active swimmers.
Cheers
Steve