This isn't extremely exciting, but about a week ago I started noticing tiny white things on my glass at night, after the lights went off. After a while they got bigger and I could see they were baby snails with stripes on their shells just like the turbos. Apparently, my pair of turbos mated without me noticing and now I have around 100 baby snails roaming my tank at night. It's actually pretty cool. So if you want to propagate something easy, get some snails.