I doubt the tray color does all that much.

ANY time there's light, water, and nutrition, there WILL be algae!

Bleach is another alternative; cheaper, but doesn't smell as nice.

--

Ray Barkalow - First Rays Orchids - www.firstrays.com
Plants, Supplies, Books, Artwork, and Lots of Free Info!
..
"dd" wrote in message
...

Thanks for the suggestion. I'll give it a try!

I've undoubted created some of the problem myself by (1) using white
humidity trays which show every bit of crud, and (2) flooding the
pots
in situ, which causes an unsavory mix of things to come out of the
drain holes: S/H particulate matter, decayed root sludge from
orchids
recently potted in S/H, algae in the S/H pots, and decomposing bark
in
bark-based media. That combines with drowned gnats in the humidity
trays to create an less-than-wonderful appearance. (I run three
fans
and use sticky traps, but I still have some gnats.)


In article , Ray
wrote:

DD,

Add a little Physan to your tray water and you'll never have an
algae
problem.