I make sure they have 2 rubber washers in them ,it really helps to seal up any little leaks .I can get them any where here .Lowes and most plumbing supply stores handle them and I get the ones with the inside screw in and outside one so I can use pvc or ABS fittings .Brass can be bad for koi and so can copper .My neighbor used them and lost his fish and only thing I could think of was the brass or copper fittings .He changed them out and has not lost a fish since .