Interracial Snail Sex

I've been de-Dallas-ing tap water for several days and saving it in big bowls and pans in order to have plenty ready for a big water change in the fish tank. This morning I finally got started, went to the tank and found this very strange growth on the glass and realized pretty quickly it was a clutch of snail eggs. Went to read up on them, and realized it might not be such a good idea to clean the tank right now cause they'll need plenty of algae to eat when they're born - went back and found the two snails above uhm, fornicating? I don't know what they're doing but it looks like fun.

And then I backed up and got a shot of both snails doing it and the results of SOMEbody's previous antics. What's the vote, should I still clean (with the gravel poo sucker upper) the tank?