They did, yes. There were 15 on that rock for about a year and a half and trust me, it was 15. I spent every day staring at it lol and then one day there was a tiny one and about 6 months later, another. I probably had 3 pop up on it over the course of its life before they unfortunately died due to an 1,100-mile tank transferWhen you kept them before, did they multiply? I have had mine for a year and the same 8 worms are in it.