First image: side view; Second image: top view; Third image: isolated close up

Any ideas as to what they are?

When I checked my 10 gallon moss/fern/lichen terrarium this morning, I found these odd new spore like growths over 85% of the terrarium. They are brown and growing on everything except bark, branches and the glass. They popped up in between barren spots in wild collected moss, but not on a large piece of moss covered bark. They are on the soil, rocks and perlite. There is absolutely no mold anywhere and the moss, lichens, ferns and ivy are all healthy.

I use organic soil, only bottled spring water and have treated very successfully with fenbendazole to eliminate fungus gnat eggs and larvae. The tank is never closed completely, but always left half open. There is no condensation on the glass. It is layered with pebbles, charcoal, fine screen and soil on top. I keep an 8 watt T5 florescent fixture on top of the tank for about 8 hours a day. Has worked just right so far.

I let the terrarium "do its own thing" basically and have mixes of wild caught moss and tiny ferns. I uprooted a "frosty fern" about a week ago as it looked terrible in the tank and would have taken over the entire tank if left to its own devices. I planted a few pieces of various rooted ivy cuttings in its place.

If someone can identify whatever these spore like growths are and confirm they are not going to destroy the rest of the terrarium, I'll leave them. I'm just afraid when these things "pop", I may have to do the entire 2 year old terrarium over.

Thank you!