Using Physan 20

[Ray]

I was reading an "algae" thread on another forum, and it was stated that the presence of algae in the pots is an indicator that the conditions in there are perfect for the plant, and is nothing to worry about.

[RGonzalez]

Originally Posted by Ray

I was reading an "algae" thread on another forum, and it was stated that the presence of algae in the pots is an indicator that the conditions in there are perfect for the plant, and is nothing to worry about.

Yes, that statement is true. But, when the population of "algae" is minimum there is nothing to concern and it can stay in the pot symbiotically with your orchids. When the population of "algae" grows considerably (which happens 100% of the time) to a point that interfere with the normal "breathing" of the roots when algae colonize the inside of the pot and roots, I particularly considere that a problem and needs judicious attention to reduce the population to a minimun as we do to any other pests.
The latter is more evident when plants are grown in transparent plastic containers which allow light past through.
For that reason YES, I use Physan 20 regularly on my orchids although I have my plants growing in clay pots.

[Ray]

I'm not sure I totally agree with that, RG.

As algae growth requires moisture, nutrition and light, the growth will be limited to the external surfaces of the medium.

In about 15 or so years of s/h experimentation, I have never seen algae invade into the interior of the root mass. I have, however, seen it coat the top surface so thoroughly that it did help suffocate the roots, but that was a diatomite experiment, not with LECA.