Green 'thing' Growing On Wood - A Fungus?

Anyone know what this is growing on the wood, out of interest? It sort of looks like those cotton/fungus things that float around outside, or even like what grows on an uneaten morsel of food in the fishtank - except for that it's bright green. I've never seen this before in the tank. NB image is 4x the size - for context, those white dots that look like balls are actually nerite snail eggs.

Thanks - does indeed look like photos of that. The female nerite snail has been spending a lot of time on the wood lately (as you can deduce from the eggs),  and it's altogether possible she may have munched sections of the growing green-hair algae before it was visible to the human eye but perhaps she didn't go over this particular section.

I've got bits of that in my tank. It looks pretty so I just leave it there. Eventually it just falls off in my tank.

(If I’m right...)

“Cladophora is a branching, green filamentous alga, that forms a moss like structure. This algae doesn't appear to be slimy. Threads are very strong and very thin. It grows on rocks and submersed wood exposed to direct light, and in extreme cases will grow on plants also. Usually it tends to stay on one spot, which makes it easy to remove. Comb it and dose more CO2. In a case where Cladophora takes over the grassy plants, mow the plants like the lawn. No algae eater is known to eat this kind of alga”

http://www.aquahobby.com/articles/e_freshwater_algae.php

Is it hard to remove? It looks like green beard algae to me. Sorry I’ve not been on the forum in a few days...

I meant to say that a green moss ball resided immediately beside the section of wood that has sprouted this green 'thing', if that has any bearing on its identification (and might indeed suggest it is Cladophora). I see that another moss ball has made contact with another section of the wood, so it will be interesting to see if another tuft sprouts.