I have been growing in coco for a few years and never ever seen moss growing on coco .
Your coco must been staying moist / wet for this to happen . Maybe watering to often ?
I dont know if its going to bad for your medium , but certainly not normal .
Cheers for the input Badseed,
Possible overwatering, I reduced watering times to once every 3 days about a week back from daily watering.
I would described the coco as moist but definitely not waterlogged, I might scrape the moss out anyway as a precaution, it's a very small amount. I'll try and take a pic before I clean it not sure it will turn out though.
Humidity in the room is around 50% ( I had to slow my fans down considerably as the humidity dropped quite low on occasions) and avg temp would be 28c, so they're going quite well in that environment.
I'm new at this and just looking to nip problems in the bud before they get out of hand