I have a fungus gnat problem with my houseplants, I've kept them relatively under control using Mosquito Dunks in my watering can since August and some yellow sticky traps but I can't seem to eradicate them. I was considering buying nematode pot poppers but I've never used them before so I was wondering if anyone had any tips for application. All my plants are still relatively small so I don't have many large pots for any of them (most are between 4-10").

Any and all recommendations welcome, having pests is really taking all the joy out of having plants. I'm in Canada so a lot of pesticides aren't available to me.

UPDATE: I figured I'd update this post incase someone comes looking for solutions and sees this. I ended up going with a top layer of silica sand (2-4 mm in size) on all of my pots. I continued with the BTI water, let my plants completely dry out between waterings, and bottom-watered most of my plants. I haven't seen a fungus gnat in about 2 weeks so I think I have been successful in eradicating them. Will update again if this changes.

Update 2: I take back the update, they're still here... I'm so over the freaking gnats.