How long do them in water? Scott's is decent but it is fairly cheap and may be where they came from. I've been doing this for a year now and have probably had the gnats for three months. So it hasn't always been a problem. I'm sold on Nematodes and mosquito dunks and will continue to use both as a preventive measure. I just repotted several plants and a few of them just had NOTHING left for roots. No wonder they're looking so bad.