Newbie under lights help?

[Keysguy]

Well, not a newbie grower but this is my first experiment into growing 100% under lights. As some have probably surmised from some of my other posts, this is my attempt at controlling my separation anxiety from my serious orchid collection which spends the summers on auto-pilot in the Florida Keys. I brought a couple mature plants home with me to try and bloom out that I've never seen before and have now picked up a few seedlings to tend that I'll take south with me in the fall where they will take up permanent residency. Getting very few new plants this winter due to COVID made the investment a very easy sell and allows me to keep adding plants over the summer.

I have a 4' shelving set-up in the basement (ground floor utility room) of our condo. I have 4' long humidity trays under the plants and noticed this morning I have green algae growing in the water in the trays. Double edge sword, right? The set-up is working and photosynthesis is happening but I really could do without the algae.

It's only been set up for 2 weeks so that algae growth happened pretty quickly and I hadn't even done any fertilizer at that point. So, I took everything apart and dumped the water and cleaned the tray this morning AFTER I had fertilized the plants.

So, my question is, I assume the algae growth is common and a positive thing but is there something that can be added to the humidity tray water to inhibit algae growth or is it just a simple case of pulling it all apart and giving it a good cleaning every couple weeks?

BTW- Plants are on racks above the water not in it. Temp runs right around 82 with 60% humidity on the rack.

Fire away, I'm all ears.

[Dorchid]

I’d say bleach or chlorine treatment.

[Ray]

Yep. Bleach is good.

[estación seca]

If the water is not in contact with your plants, I would leave it to grow algae. You should dump it anyway from time to time, otherwise even more salts will build up in the trays. The algae will outcompete and likely inhibit harmful organisms like water molds. You need to put in some mosquito dunks. Being an environmental clean freak is a great way to promote infections in most organisms.

[Keysguy]

Bleach sounds good. Wasn't sure if that could evaporate up into the leaves and do damage.

I'll try a very small amount and keep an eye on it.

Thank you all!

[MJG]

I grow my orchids under lights, on humidity trays (deep ones, lots of water).

I don't let my watering runoff go into the trays. I water each plant over a bucket. I think it reduces the amount of organic matter in the trays.

The other thing I do is add physan to the watering can that I use to top up the trays.

I have had no problem with algae or nasty water. Once in a blue moon I clean the trays and rocks and replace the water.

[Keysguy]

I think it reduces the amount of organic matter in the trays.

Ah, of course! Duh.....the organics from watering runoff never crossed my mind. The fertilizer and other matter was already in the pots! That's what got it started so quickly.

You guys are great, I've never once worried about what happens to the stuff that hits the ground. This "closed loop" kind of approach is all new to me.