About a month ago I had hundreds of colonista snails in my nano and the back glass was literally covered with spirobid worms. Over a matter of a few weeks all of the spirobids disappeared and most of the colonista snails as well. I've noticed they appear and then disappear a few times a year. Just curious if anyone knows what causes these cycles of population explosions? I haven't changed anything as far as feedings or maintenance and my parameters are pretty consistent.