what kind of system are you using?. I have rockwool and hydroton in net pots and I keep the water level at about the bottom of the the basket. I started out with 6 diffent clones I got at 3 different medical dispensaries. These were all barely rooted out in a small amount of soil. I knocked as much of the soil off as I could and transplanted them into rockwool. One of these plants had root aphids. The root aphids killed one of the 6 clones before I spotted them and were basically preventing the others from rooting out.
I have about 10 gallons in my DWC, and I just threw about 1/3 of one doughnut in there and let it float. I hand watered the plants a few times after the doughnut had been soaking for a few days just to get the bugs above the water level. I added another 1/3 about 1 week later and hand watered a few more times. It did not seem to have any impact on the water PH and it did not have any negative impact on the plants. Within about 2 days of the first mosquito dunk, there were thousands of dead and dying bugs that had crawled out of the hydro sytem and onto the floor where they were twiching in the throws of death. This made me very happy.
My DWC system is home-made out of one large "under-bed" style plastic storage container. It has an aquarium air pump and some bubble stones. It also has an aquarium water heater set on 60F. There is no pump and all the plants are in the same resevoir together.
You can crush them up or throw them in whole. I don't think it really matters. You'll probably have to treat them 2 or 3 times over several weeks to kill the bugs and the unhatched eggs.
Mosquito dunks claim to be organic and pet-safe and safe for use in planted aquariums or in goldfish ponds.
Here is a
View attachment 1329356picture of my legal medical grow and a picture of the roots of my smallest plant (one that the aphids had nearly killed less than a month ago).
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