I set up a tropical tank last year, and we had a lot of pregnant livebearers, but never any survivours, despite plenty of plants, rocks, wood etc.
So we asked for a clump of moss for the fry to hide in.
We were given an unattractive dark green cloud free of charge. It looked horrible so we put it behind the other plants and that was that.
The fry did start to survive, and the bottom feeders loved it.
Eventually though, it began to spread. At first it just rooted into crevices on ornaments, but eventually everything, including the glass, was carpeted in it.
To cut a long story short, we eventually had to replace everything, which was expensive and inconvenient. We removed all the moss/algae, the only way to get it off the glass was with a razor blade.
We have a sand bottom and it doesn't seem able to grow on that.
It has come back somehow. Its growing on the leaves of new plants, my heater/filter and air bubble things as well as my thermometer are carpeted in it, and Im getting to the point of hating the tank. It used to look lovely and now its awful, we're very tempted to get rid of it.
This plant is no more than 1cm thick were its now growing, but it roots on very wel and tough to remove, even with a blade. Its very thick and dark green, and look like fur. Ive looked at Java Moss and Hair Algae on google. Java Moss doesn't seem to be a problem for others, and the hair algae looks a lot brighter green than what we have here.
I really don't know what to do about it now.
Any tips/help identifying would be much appreciated