Don't know how it happened but it seems I accidentally got some fissidens fontanus in my 220g and it found my DW. I noticed a small fern looking moss months ago but it was so pretty I didn't give it any thought. It seemed to spread slowly on various spots on the DW but recently I increased my dosage of glutaraldehyde and this Fissidens is spreading like a weed. At the rate it's growing it's going to spread over the entire large piece of DW. I also noticed today a small area is starting on the largest piece of DW and I didn't put any there. I can only assume a tiny piece came in on a plant and established on the DW. Does anyone grow this? Any info or insight on this moss? The yo-yo loaches like to groom through it so it stays very nice looking but isn't it rather strange that it just appeared out of the blue growing on a piece of DW in the tank.