My experience in semi hydro...
 

I've been experimenting with s/h for about three years, and nowadays I am in just-put-anything-I-buy-in-S/H-unless-I-know-better-mode. ;) Instead of LECA (which is strangely hard to come by in S. Korea) I am using a mix of large chunks of lava rock, pumice pebbles and large perlite, (sometimes just with pumice pebbles) and it worked nicely so far...lava rocks and pumice both have tons of small holes which holds water well so it is not surprising.

I found that Dendrobiums in section Latouria and Formosa are mostly perfectly suited for S/H; from what I know they require even moisture year around so they are the perfect candidatsles for semihydro culture. I almost lost a mounted den. bellatulum, but I managed to save it by converting it into semihydro culture. Since then I have been doing S/H more than ever. Hell, I am now growing my lettuces in large gravel and pumice mix sitting in a shallow tray of water!

Of course there are exceptions and my environment I found Prosthecheas and Encyclias are somewhat less successful with S/H. My Prosthchea (syn. Euchile) mariae resented to be in constant moisture, and ironically began to grow when I put it in a mount without any moss around the roots. Remember, I almost lost my mounted Dendrobium bellatulum which I managed to save by converting it to S/H!

Each individual's environment is different, meaning the plants that can be easily grown in any particular method varies.

Many years ago, I imported about 500 "Chinese" cymbidiums per month from Taiwan. Over there, they were grown in a form of S/H culture using a mixture of pumice rocks and tree fern and were watered daily with diluted spoiled milk as the only nutrient.

My Prosthechea radiata is a total beast in semi-hydroponic culture, probably the poster child for the technique in my collection. It's flowered strongly each season, and each lead produces 2 new ones like clockwork the following season. And I've killed enough Dendrobium that I don't even bother to try them anymore. Different conditions, different results!

Diluted spoiled milk?!? Bet those were fragrant when received. Yuck.