I wondered that, have looked uber carefully at the fish, but can see no hitch hikers.
I did mention it at the lfs, the guy said they can show up if over feeding? I`m very careful with the feeding, only feeding them once a day, and only as much as they will eat in a few mins.
Ammonia and nitrite are at 0ppm, and the nitrate is only 10ppm now, so the filter and tank are maturing nicely now.