Green moss growing in orchid pots?

[Tickolas]

Hey guys,

I've just noticed this weird green moss growing in the pots of my three orchids. These include one phal, one dendrobium nobile and one lime-green phal lookalike with thick blossoms. I've watered all three about every ten days, every other time with some fertilizer, letting the water drain out through a hole in the bottom of the glass pot.

I think the phal lookalike came with green moss growing in the topsoil when I bought it from the local flower shop. I've just now repotted it with all fresh soil. I also repotted the phal and rinsed off the roots and pot thoroughly. The dendrobium has such dense roots though, and I'm not sure I can easily uproot it without doing massive damage to it.

Any suggestions on what this may be, how to combat it and prevent it happening again?