I have some algae growing in inorganic based media with my seedlings as well. I haven't seen any bad effects. It makes me feel better knowing that I have enough moisture for the seedlings...but the humidity is significantly lower here. Doesn't seem like it should be too bad of a sign. Unless of course if it starts growing on the seedlings as well? How moist is your media?

Some of the sphagnum is quite damp and some not so damp, but the humidity is quite high in all cases. I have no algae on any of the pots that have peat moss, it's only on the sphagnum.

A little bit of algae is no problem, but when it gets out of hand it can almost seal off the surface of the moss, preventing good aeration and water penetration. Also, if your seedlings are slow growing, like Vrieseas, Guzmanias, etc., the algae will outgrow them and can actually engulf and smother them. *Not* pretty. :-(

I give my seedlings an occasional spray of Green-Shield (diluted, of course). I generally mix it with a foliar fertilizer so I can feed the seedlings while killing the algae. It's not 100%, but it does help keep it under control.

Here is a link that might be useful: Green-Shield

Lisa, thanks for the info and the link.

Consan Triple Action 20 is another good product available in box stores across the USA. It is used for everything from molded walls. refrigerators to bromeliad seedlings. Not expensive since its only drops on most plants. During IKE recovery I am sure millions of bottles will be used.