I have way too many orchids all in LECA on windowsills of south facing windows. I have only lost one or two on transfer to LECA mostly I think due to when I made the transfer. Following Ray's advice I now try to only transfer most orchid varieties after flowering when new root formation is happening. I also use KLN rooting hormone and keep the plants on a seedling heating mat for at least 2 weeks (also something I think that Ray recommends). However, in my experience Phals transfer just fine even when blooming. This winter I have had some problems with established Phals that I think are related to how cloudy and cool it has been in my normally warm and sunny apartment. I am trying to remedy this by using heating mats and so far that does seem to be working.

Karen451, thanks for the reply. I'm wondering if I keep my house just too cool for using s/h. It's usually 70 during the day, and down to 62 at night. To compensate for the cooler temps, I have also been keeping the plants on seedling heating mats. They still seem relatively unhappy. I'm trying to decide if I should persevere, of if it's likely to be a no-go with the temps in my home during the winter.

I've only tried a couple of phals in S/H and lost them. However, every oncidium I've ever put into the stuff grows like gangbusters. Sorry I don't have any pertinent advice.

I dont think that your temps sound too different from mine in winter and I would think that the mats should help, but I defer to others on that question (bear in mind that you actually need a drop in temps to get some orchids to bloom). But going forward, your description of your plants makes me think that root rot has set in. I would take one plant out of its pot and check. I would cut off all the black and soggy roots and then put the phal back into clean LECA. I would then treat with KLN at the concentration recommended for Rockwool, and keep the plants out of the sun but on a heating mat for at least 2 weeks.

In my experience, you need to keep phals in S/H at least at 65 degrees or higher. Mine really struggled when the night temps dropped below 65. In fact, I've moved all of my phals out of S/H because of the winter house temp issues.

They did great in S/H other than the cold winter temps.

Good luck,

Bob

Given the issue that the roots might be kept too cold with the reservoir at the bottom causing evaporative cooling, what about just using the PrimeAgra alone, in a regular pot, rather than a s/h pot?

Many people use primeagra as a potting medium alone outside of S/H. Or at least hydroton (cheaper). People love to use it particularly for plants that like a ton of air at their roots/ really like to get dry quickly like Vandas and assorted hybrids

I'm a late to the party, but try insulating underneath the heat mats. You can lose a lot of heat down through the table if you're not careful.

Here is a link that might be useful: Amzn reviewer explains about insulation.