Snails are taking over my fish tank. Tonight I came home and they are all forming this weird snail mass. I broke them up, and they reformed. What the heck is going on, and how do I cut down on my snail population? I'll be draining most of the water out of the tank in a week or so, so I plan to try to catch a bunch and dispose of them but is there anything else I should do in the meantime? Perplexed!