They sell fish aquarium sealant, my Pet Supermarket, Petsmart, and sometimes petco have it. I suggest a good solid wash before anything. Have you tested the tanks? The brand i've seen pop up is Marineland, but I am sure there are others. Some say you can use SOME types of regular sealant, but I always go the safe route and use aquarium. Perhaps a more experienced Aquarist will be on?