Physan 20
 

I didn't know physan could be so harmful. I mixed maybe half a teaspoon with some water in a small glass and applied some to a root tip that had some mold on it, and it certainly did take care of the mold... as well as dissolve some of the root tip away!

I think my s/h case has gone from bad to worse. that root was looking pretty good, it was maybe a half inch long and I was thinking it would be adapt and grow well into the S/H and would become a main root, but now I have my doubts. The only roots I have remaining are two semi brown ones that are older and didn't completely die during the transition, and some nubbins... some of which have stopped growing. Though b/c I have a new leaf coming, I figure it's not all THAT bad??

I limit my use of Physan to 1 teaspoon per gallon. Your mixture is probably 20x that concentrated, and it IS, after all, a mixture of quaternary ammonium salts.

Physan 20
 

I don't do hydroponics, but, I know Physan is very concentrated. A drop or two in that amount of water would have been plenty.
I have used it in the past mostly to spray my amaryllis (hippeastrum) when they are just sprouting in the early spring. They get a rust that, if not contained, keep the plants from flowering. I only put maybe a teaspoon in the spray bottle for this application.
You can always use a slightly stronger concentration if you see the weaker does not quite do the job.
And the old saying, "if all else fails, read the instructions". I just bought a new bottle and there are quite extensive instructions included.
Beverly A.

Yeah, I mix 1/4 tsp with 32 oz water in a spray bottle.

Physan is the same as the algaecide sold in pool supply houses. (It is much cheaper there as well)

For a pool the rate is 20 ounces to 10,000 gallons so keep this in mind when using it on plants.

Once you damage the growing tip of a root it will never grow again (but the root will still support the plant). The plant will however put out new roots. be patient.

Jerry, that is a most interesting comment about pool algicides. Here in England, our authorities conspired last year with the EU to ban Physan sales - worse than that, vendors were instructed to destroy any remaining stocks (but I have no idea how they went about that safely).
We are all still looking for a viable alternative . I have a swimming pool, but would not like to use any pool algicide on my orchids without further input. Do you have, or can you direct me to, any information/experience at all which would help me (chemical constituents I should look for etc)?
We really do need to find some sort of viable substitute for Physan which was a brilliant product so the pool chemicals sounds great to me.
Richard

Pool algaecides are not the identical chemicals, but they are quite close, and are effective, but then again, so is household laundry (chlorine) bleach.

You used well too much of Physan 20.To know for sure how much you should use for different problems go to Physan 20 and there are 13 pages how to use it and for what.good luck:goodluck:

Ray

HTH brand and several others are the exact chemicals as physan. You can compare the labels.

HTH is 50% stronger than physan but that just makes it even cheaper.

I should have been clearer that not all algaecide are the same, but there are several that match Physan exactly.

Good to know, Jerry.

Thanks.