Thanks buzzed, I'll have a look at that site.

Prices do not seem that bad; how much is needed per large pot ? Are multiple applications required ?

I prefer hypoaspis miles for gnats. Get some of those and your gnat problems will cease. They can also feed on other things in the soil to sustain life when there are no pests to feed on.

Hypoaspis miles

The package that I got was 15.00 usd and it covered 1600sqft, I just put a little in my one gallon feeder, per pot and feed, did not measure it. If you do get it put it in your refridge right away. I really like this stuff, have not seen any knats in awhile, I'm sold on it, plus no chemicals. good luck.

GB, why do you prefer these over toadies ? Followed the link you provided (thanks for that!), and from what I read the mites also kill the notorious spider mites. That alone is a good reason!

Honestly, never tried nematodes. I never even purchased the h. miles I had either. I figure they came with some compost or soil I got (as can gnats.) Either way, I noticed the h. miles shortly after I started noticing some gnats. I'd say that within a week the h. miles population was at it's peak and there were no gnats to be found. As far as them eating spider mites goes, my opinion on that is rather low. I am sure they would eat mite eggs and such, but they would have to be in/on the soil for the h. miles to get at them. Usually not too many spider mites hanging around that area of your plants. I have used Phytoseiulus persimilis for spider mites. A dosage of azamax a couple of days before releasing a bunch of these can wreak havoc on spider mites. TBH, I am not sure it is necessary after using Azamax.

ok, thanks GB for the clarification on that.

alright folks here is a way to win the battle against a fungus gnat infestation. IVE HEARD/USED DIFF METHODS LIKE USING PLAY SAND AND PERLITE.. THOSE METHODS DID NOT WORK FOR ME IN THE PAST. SO I DECIDED TO TRY SOMETHING ELSE..I decided to use diatomacous earth. it worked.
DE is avail at lowes for $ 9.00

As with any war and playing dirty you carpet bomb..... AND WAIT TO SEE WHAT HAPPENS..(just kidding)
so the first step in this battle is to make a slurry. i used 1 tbs of DE and 1 tsp of molasses per gal of water so it traveled through the soil.why molasses? i'll explain that soon.
step 1. dust mask/sunglasses.( this shit will dry you out and agitate your nose and goop up your tear ducts)
step 2. make slurry
step 3. apply slurry and molasses mixture.
step 4. take a wire collander and place DE in it.
step 5. gently tap the side of the collander and apply DE generously to the top of the soil it should be completely covered.
BOOM!! the initial attack has been launched.. basically the DE in the slurry saturates the soil any pest that ingest it will die within 24hrs not to mention the DE shards are now completely embedded in the root structure itself. this makes it extremely painful and causes external and internal injurys to said larva eventually leading to death. the DE on the topsoil literally acts as a barrier and fungus gnats trying to get back into the soil are dehydrated and also cut to shreds due to the DE sticking to their bodys also it shreds any flys trying to escape the soil. the molasses is also a key ingredient the pests get strung out on sugar and become hyper active hastening their own demise..
also it seems that the springtails in my soil were not effected by the DE even though the fungus gnats were, THERE WAS NOT ONE NEGATIVE SIDE EFFECT TO THE PLANTS THROUGH THE APPLICATION OF DE HAS OCCOURED AND I WAS VERY GENEROUS WITH THE DE.
FUNGUS GNAT INFESTATION INDOORS ARE NOT YOUR FAULT. MOST INFESTATIONS START AT THE SOURCE.. ie manufacturer or storage facility like hydro stores.