Gnats are a pain in the ass. I found APTUS Soil Attack is very effective but I have no idea if it would harm plants as your thing did. However, in your case, I would rather change the substrate and wash it with H2O2.
Gnats are a pain in the ass. I found APTUS Soil Attack is very effective but I have no idea if it would harm plants as your thing did. However, in your case, I would rather change the substrate and wash it with H2O2.
I am sure it would be safe outside of the seedling stage. This stage is very sensitive to anything like that.