So today I noticed lots of fungus gnats in my grow lights and in my plants, many of the plants I've let get dry as fungus gnats like damp soil but other plants like my Boston Ferns like damp soil along with some other plants I have. They are indoors and outside, they are everywhere and I need to get rid of them before they destroy my plants.

I have researched how to get rid of fungus gnats but keep reading lots of random things that might or may not work. I need to find a solution that works to get rid of them once and for all.

One thing that keeps popping up is BTI which isn't available here in the UK, I have been using neem oil but I've read that neem oil isn't really effective on fungus Gnats.

What is an alternative to BTI?

What will kill fungus gnats that is safe to use on plants?

You can't control fungus gnats by trying to kill the adults. They don't feed, just lay eggs and die. But, you can control the larvae. Find an insecticide with Pyrethrins as its major ingredient. Spray the soil surface every few days. It will kill the larvae as they emerge from the soil.

Use small pieces of mosquito dunks: https://www.amazon.co.uk/Summi...
soak in water overnight and use that to drench. It contains BTi. Destroys the larvae. Use it several times when you water. Also get your watering under control and let the top dry out really well. Fg cannot live in dry soil. I would let it dry out deeper in the soil too. The longer the soil says damp at the top the more likely FG will come back. Also have a fan running to circulate air.
You can also set up sticky traps as additional defense against the flying ones so that they do not lay eggs.

Thanks. I'll order some mosquito dunks today. I'm still on the hunt for an insecticide with Pyrethrins.