I recently ran into a problem that I seem to be having some difficulty resolving. I run hydro-buckets that are top fed by drip rings. A couple weeks ago I found fungus gnat larvae residing within each bucket. I did some research and found that beneficial nematodes would help resolve this problem, however all cases discussed pertained to soil growing mediums (I use expanded clay balls). I obtained some nematodes from my local garden shop, and following the directions exactly I treated my plants. I kept the nematodes refridgerated I applied them in the dark I mixed the nematode mix with water to apply I waited for about a week before I checked the fungus gnat situation again, this way the nematodes were not exposed to any more light than necessary. Unfortunately when I did check, the fungus gnat larvae were still present, however their population had declined. I was wondering if anyone has any experience with fungus gnats in hydro systems, or with nematodes in hydro systems, and may have a solution for my problem or an idea of the effectiveness of nematodes as a biological control in hydro systems.
I also failed to mention that I have sticky fly paper set up throughout my room and on top of the buckets. I have not seen any adult fungus gnats on any of these sticky traps.
I have not used nematode, just heard about it but a friend told me to keep a pan of soapy water in the room. The gnats like the bubbles, they fly into it and drown. My water is always full of gnats,it works. What I don't know is if they have already laid their eggs.