how to reduce algae growth on surface?

[maxjohnson]

What do you to to prevent green algae from growing too much on the surface of potting mix? What do you spray on the surface and not harm the seedling and germination rate?

[worth1]

10 percent solution of home use hydrogen peroxide and water in a spray bottle might help and it won't hurt the plants.
It will also stop damping off.

[Cole_Robbie]

I usually cover seeds in vermiculite to sprout them, and then having the top layer of media be loose and dry helps against algae. Perlite or sand would be similar. And bottom watering also helps.

[bower]

I always take algae as a sign it's too acid - sprinkle of lime works.

[AZGardener]

I moisten my seed starting mix with boiling water. I then water seedlings with bottled water until they are planted in the garden. It has solved gnat and algae issues. I've also moistened the seed starting mix, then bake it until the internal temp of the soil in the pan reaches 165F or 73.8C HTH

[zeuspaul]

I don't recall having an issue with algae. I use well drained sifted recycled potting mix with added sifted perlite and worm castings---no sterilization--no domes. I pre germinate and then place under grow lights. I top water. If it's sunny (almost every day) and not too cold I carry the trays outdoors and place in the sunshine, then back inside at the end of daylight.

[karstopography]

I haven’t had issues with algae either. Absolutely no domes for me. Jiffy soilless seed starting mix as a top layer, Baccto premium potting soil below. Top layer will show signs of drying out a bit (color change) and trays will lighten up a bit before I add additional moisture.

Trays go outside on warmer days, top water only if necessary, mainly heavy misting or gentle sprinkling outdoors.

I don’t keep my trays in a dank basement either. They are either outside weather permitting or in the garage, but either way, there’s plenty of air circulation and sunlight on them if possible.

[GoDawgs]

Like @karstopography I grow all of my seedlings just a tad on the dry side. Not really dry but if the containers start feeling a little light I water from the top sparingly. No gnat or green problems. They are grown indoors under lights and then hardened off out on the front porch when it's time.