I would only mix a capfull or two with a bit of soap for 40 gallons of mix. I never used it at high levels, nor did I spray it on my plants. I washed them down with water and let them dry before I put them back under the lamps. The preditor mites was the real exterminator I suspect. They dont harm the plants. The dont build webs and once they eat all the spider mites they eat themselves so no worries.

One love
c