I don't know if my hydrogen peroxide spray bottle would help or not. You could mix some up and try it on just a spot and see what happens. 1/4 cup drugstore 3% hydrogen peroxide to 2-1/2 cups water (1:10 ratio H2O2 to water).

Maybe someone will come along with the exact right answer on this one. I can only speak for myself, but the solution isn't likely to hurt the seedlings whether it works or not so I'd be inclined to try it were they mine. Have read that a little is good for them, don't believe in overdoing things, but might take a couple apps if it works.

I get moss and have read reassuring posts that it won't adversely affect the seeds or plants. The solution doesn't get rid of the moss for me.

Maybe venting them a little better will help some, but once something starts, hard to stop it, maybe won't hurt one bit.

I am so glad you asked this question. I have noticed the same and just assumed that those seeds would be lost.

The hydrogen peroxide solution could probably help, but the algae won't hurt the seeds/seedlings. They'll grow happily right thru it.

I agree, the algae isn't going to hurt, happens pretty commonly here where winters are mild and wet. In fact, most everything turns green in winter here, you should see my north facing deck right now :(

You don't say what zone you are in, have you taken tops off your containers yet? Usually some circulating air, bit of sunshine slows it down but it shouldn't hurt your seedlings, it's not the same fungal enemy as causes damp off.

Thanks for the advice!! I am so glad to hear that my sprouts should be okay!!

Last year my containers had algae and did fine. So far this year I haven't noticed any though I did make certain my drainage holes were actually holes and not just slits.

-StLGirl