if you do fresh, don't go with lobsters, they'll eat your fish if they can catch them. Or you'll find rips in your fish's fins. Or the fish will eat them when they shed their shell
question about buffalo heads, i was looking into them, i have 7 yellow labs 1 blue johanni and a featherfin. well first i have a 75 gallon would they be compatible with my fish and how many fish do you think i could stock.most fish are about 2- 2 1/2 inches