I'm not sure if this is the best place to post this question, but most of the cyanobacteria articles seem to make it here...

I have a 10g packed to the brim with a few months growth of chaetomorpha, to the point now where it's trying to grow above the water line

I was originally planning just to take off about 3/4 of it, divide it up and give it away, but there's a few bits of cyanobacteria growing around the top near the surface of the water. I knock it off, but after a week or two it's slowly creeping back and I knock it off and flush it again. It's not much, and I'm not really worried about it as It's not a display tank, but I was worried that if I gave away some of the chaetomorpha that it may infect other's tanks. Does anyone know if this is something to worry about?

As well, there's a few small tufts of GHA growing around a few edges that I leave for the snails to munch. I won't hand out that bit, but is there a chance that 'spores' or something from the GHA may hitchhike to another tank?

It's possible, but with cyano it's in their tanks already and just needs the right conditions. Most likely the GHA as well, but since most people put it in their fuge then it should be ok since most fuges have all kinds of algae in them. I'd put up a disclaimer just in case though, but I'd doubt that anyone would care...

Hmm, I'll probably do that. I've a spare five gallon gathering dust, I may use it to experiment a bit...