Well, as you have already found out, mixing two different species of clowns in the same tank does not often work out very well. The simplest way to keep them apart temporarily would be to get a piece of eggcrate and cut it to make a divider, that should help. As to catching the clown, try using a modified 2-liter bottle, I've caught just about every fish in my tank this way. Cut the bottom of the bottle, just above where it curves, leave about 1-1 1/2" to make a "hinge". Then take some fishing line, put a small hole near the base of the bottle and then to the hinge, you now have a small trap. Put the bottle in your tank, make sure to press the hinge a little to keep it open, place some food in the trap, when your clown goes in, pull the line and boom, you have your fish. It will take some patience and you may need to leave the bottle in your tank for a day or two to get the fish used to it, but it will work.
HTH
Allen
