If there's a way to prop up the end of your catch-tray and tilt it so that it drains fully, without cracking the tray, do it. And if you can get in there and manually run a fishtank cleaning brush around the crevices to dislodge any eggs or larvae, that would be a good idea too. You might have to support the underside with a sheet of plywood if it is not strong enough, but most commercial plastic should be.