Massive repot
 

Hello
I am planning to repot all of my plants due to a fungus gnat infestation. I need to purchase new potting material and wanted to ask about orchiata.
I have
3 standard cymbidium,
two phal and a mini phal,
3 small cattleya and one large.
1 Paph Maudiae (recently bought and not doing well)
1 ang seq.
1 oncidium
I realize there isn't a one size fits all material with this variety but any suggestions are helpful.

I like Orchiata a lot. The fact that it comes in rather precise sizes is helpful too. I like the largest size for Catts that are mid-size or larger. (Super) For everything that needs good drainage but wants a bit more moisture than the bigger Catts, the Power or Power + size is perfect. For the Paph and Oncidium (and Cyms if you want to) the small size (Classic) is good. Since Cyms are forgiving (and use a lot of bark) I use generic seedling bark rather than expensive Orchiata...

Whoa. You're about to undertake an enormous effort for nothing.

Fungus gnat larvae live on organic matter in your medium. If you repot all your orchids into medium with any organic matter, you will still have fungus gnats.

The easiest way to get rid of them is to set a fan blowing across your collection. The adults are weak, and can't fly against any breeze. As the larvae hatch to adults, they will be blown away from your plants. The adults will not be able to make it back to the plants, and will not breed any more. The eggs and larvae existing in your plants will eventually hatch into adults, which will be blown away from your plants. Soon the fungus gnats will be gone.

Some people douse their pots with insecticide. This can work, as well, but I would rather use a fan in my house than use poison in my house.

I've used sticky yellow fly papers to great effect. I had an infestation last year, left the papers for a couple of months and they were gone.

If the medium is breaking down the it's time for a repot. If the medium is still good, you can also use Mosquito Dunks...they come in granules too. Put about a tablespoon of the granules (I don't know the conversion rate) in about a gallon of water and let it soak for a day or two and then pour that through the pot. You'll have to do it a few times but that will take care of the fungus gnats and it's not harmful like most insecticides.

Side note...use up the soak water because it doesn't store well for long periods. It gets very slimy and smelly.

I have had fungus gnats for ages they are in everything. I have tried everything under the sun to get rid of them, fans,stickies dunks letting the plants dry out completely...everything... I am pretty sure they are killing my paph. I've reached my limit and decided to purge everything ( including the house plants in soil) right now im using cocoanut husk clay pellets perlite and some spag on top. ive had bad experiences using bark in the past but the orchiata looks like it might be a better choice.

Try hot, soapy water as a pour through. I also have had success spraying Bayer 3 in 1 on the soil surface of potted plants.

You will not likely get rid of them by moving to another organic medium. Larvae and eggs will be attached to the old potting mix on the roots, and it is highly unlikely you will be able to remove all of them.

Paphs do well in semi/hydroponics with nothing but LECA. Nothing in there for the gnat larvae to eat.

I had a pretty epic fungus gnat problem last year. Between sticky tape, placed in the worst areas, and switching a large portion of my collection to S/H, I have seen maybe a handful of gnats this year.

Gotta agree with what's been said here.

I think that your medium is too wet, too broken down or both.

I had an outbreak, but when I switched to mostly mounts they went away, because they can't stand the regular drying, and also in the summer all the doors are open, and any breeze zips thru the tunnel and as Estacion seca says that blows the adults out of the greenhouse. I certainly haven't noticed any this last year or so.