I've had most of my orchid collection in semi-hydroponics for around 4 months now. The verdict is that my orchids seem to love this method of culture and, well, I mostly do, too. Mostly. It does have a few shortcomings. For one, it is a pain in the rear to completely drain the old solution out of the pots, cover the drainage holes, fill the pots to the brim with water, and then drain them completely to flush out any salt build-up or decaying organics. This process takes a long time and I almost always end up accidentally losing some of the LECA into my drain bucket which means I have to collect and eventually resterilize them before they can be used again. The other problem is algae. Because I used translucent containers (the better to see the fluid levels and growing roots through), a lot of light gets into the moist, nutrient-filled space and algae runs rampant.
I've had a solution to these problems in mind for a while now that I recently decided to finally put into action.
Instead of using a single translucent container with two drainage holes on the side for each plant, I'm now using a translucent container with many drainage holes in the bottom that is placed into a mostly opaque container with no drainage holes. To make the outer, mostly-opaque containers, I used the same plastic deli containers I bought the last time, taped off a window on the bottom so I'd be able to see the fluid levels in them, and spray painted them with two coats of Krylon Fusion. After the paint fully dried, I peeled off the tape and set about repotting my orchids. It was a huge hassle because I didn't have enough sterilized LECA or spare containers so I had to do several rotations of unpotting, cleaning out containers, poking drainage holes in the containers with my cheap soldering iron, repotting into the containers with clean LECA, then sterilizing all the used LECA I'd just collected. In the end, though, I'm certain it was worth it.
The new system should significantly reduce the amount of algae since the opaque outer containers will block most of the light. The window on the front of the outer container will still let me see the fluid level and, if I want to check on the roots, all I have to do is lift out the inner translucent container. Pot flushes will now just be removing the inner pot, dumping out the fluid in the outer pot, replacing the inner pot, filling the pots to the brim with water, removing the inner pot again, emptying out the outer pot again, replacing the inner pot again, and adding some nutrient solution. That should be a lot quicker and result in no lost LECA since the inner, LECA-filled pot won't be tipped over.
I am so please with semi-hydroponics that I'm actually experimenting with converting a few non-orchid plants over. Right now, I have a Nepenthes sanguinea, a Hydnophytum papaunum, a Myremecodia tuberosa ‘papuana’ “Pink Fruit”, and a Squamellaria wilsonii in my modified semi-hydroponics setup. These are all epiphytes like most of my orchids so I'm optimistic. If this goes well, I'll try converting most of the rest of my Nepenthes and a few other myrmecophytes. I've also heard that Hoyas do well in semi-hydro and I'd be willing to try a few of the epiphytic bladderworts and maybe my struggling Heliamphora minor.