Is there a lot of rock in the tank? Any fish can be removed within half an hour if you want to get quick and dirty about it.
Drain about a third of the water into clean buckets. Remove the rock from half the tank into the buckets, essentially opening up half of the tank. Drop a clear plastic container or tupperware bowl into the tank in one of the open corners. Use a net to herd the fish into the container. It may take a few tries but the fish will instinctively seek cover and eventually go into the container rather than return to the other side of the tank where the net is. Works every time. You can mess around with traps and trying to net the fish while the tank is intact, but you're going to become really frustrated, IMO. If it's a reef and you have corals to remove/move, it's more of a hassle but worth it if you want the fish out bad enough.
hth
