Algae in Semi Hydroponic system

[Zoren]

Good evening members, I have been very busy lately and have no time to check in to see what's going on.
I have developed a problem with algae. 1) Is algae Bad,Good or tolerable in SH growing? 2) If Bad, how do I get rid of it (without re-potting) every time it grows? 3) Ounce I get rid of the algae, how do I either stop it from growing again or control it? 4) I have read that Physan 20 and bleach can be used (separately of course). Will these applications work to kill the algae and control re-growth. Of course my main concern is that this application method Will Not Kill my Orchids. I know that my questions should be addressed to SH growing only, but, rather then starting a new thread will these methods of work on all Orchid growth mediums. It would be greatly appreciated if one of our senior members could give me some help. Actually any member with an answer would be great. Thank you, waiting for somE answers and direction.HELP!!! waiting for some answers and direction....Zoren...

[SillyKeiki]

Algae only need two things to grow: light and constant moist, so unless you can take out of the equation any of those factors, you are going to have algae.

Of course we cannot take out the moisture, as our orchids need water, but we can take out the light. Using dark, or opaque pots always works. You can still use a clear pot if you want to have a look at the roots to check everything is fine, you only need to place that pot inside another opaque pot to stop the light from reaching inside.

The algae problem, in my experience, however, is mostly aesthetic. They only really grow on the walls of the clear pot, somehow they don't like growing on the clay balls, and they definitely won't grow in the inner parts of the media, because light doesn't reach there.

One of the few things that would worry me is the build up of waste substances due to the decay of those same algae. However, this has an easy fix. I periodically (once a month) soak the pots for about an hour, then flush the water out thoroughly. Decomposing matter as well as excess fertilizer will go away.

Very fine roots like oncidiums might get suffocated if there are a lot of algae growing on them, but that doesn't happen that often as they usually have many other roots.

A different issue might be the smell. If you have many, many dead, decaying algae it can start to smell bad. Or so I have heard. I have algae in my pots, but it has never smelled badly because I flush regularly.

I hope this helps.

[Ray]

Actually, algae needs THREE things: light, moisture, and nutrition. Excess algae growth is usually a pretty good indicator that you are overfeeding, especially if your fertilizer formula is high in phosphorus.

Trying to eliminate the algae "in situ" is difficult and not a particularly good idea. Even if you are successful without harming the orchids, you leave them growing in a mess of dead tissue. The most practical approach is to not worry about it until you repot into a clean pot, then stick the old one in the dishwasher.

Prevention is really the key, and that can include the use of opaque pots to avoid light intrusion, but I really believe that reducing your fertilizer concentration is the key. You can augment that by monthly treatment with Physan (1 teaspoon per gallon) or chlorine bleach (1 ounce per gallon).

For what it's worth, when I switch to using K-Lite at 25 ppm N, my algae issues vanished.

[SillyKeiki]

Algae need very little fertilizer if anything at all, that's why I didn't mention it. You don't even have to fertilize to have algae. At least in my experience.

[Zoren]

Ray, will the physan 20 and the bleach help control the algae until I re-pot? Or, would it be better to re-pot the SH containers that have the algae? Either way I will reduce the amount of fertilizer I use. I also would like to know if the Klite fertilizer I have (the label says to use distilled or reverse osmosis water) will still be effective in tap water (ppm of between 145 to 175 ((water department readings)) do I have change the amount suggested on container or use a different fertilizer (I have other fertilizers). Do you have a Klite that is formulated for tap water? I am thinking of painting my containers to reduce the amount of sun rays, do you think that idea will help me with my problem. Looking for your reply....Zoren... P.S.- Thank you Silly Keiki for your input....

[WaterWitchin]

Zoren... I personally wouldn't paint your pots. Slip them into a slightly larger opaque pot instead. Part of the "fun" of semi-hydro is the ability to easily see root growth.

Ray is telling you that excess nutrients will increase algae. In a pond or waterway, an excess or increase of phosphorus and nitrogen create an algae bloom (along with lack of turbidity and temperature stratification). The oxygen in a S/H reservoir, if not properly flushed, leads to anoxia (oxygen depletion), which also creates an uptick of phosphorus and nitrogen, creating a larger algae bloom.

Thus, less fertilizer, more frequent flushing for awhile, will help lower the phosphorus and nitrogen in the reservoir. So, less algae bloom because less excess nutrients.

And that's likely more than you wanted to know about algae, but I couldn't help myself.

[Ray]

I agree. Ignore the algae until it’s time to repot.

[Zoren]

I would like to thank all of you for your suggestions and advice. I will be trying most or all of your suggestions, I will keep all of you informed as to my progress...Zoren...