How to prevent mosquitoes from breeding in my swamp cooler?
BT ( bacillus thurngensis ) will kill insects . It is not a biocide so will not affect animals.It kills anything with an alkaline stomach and has no affect on anything with an acid stomach like an animal. Commonly available at garden shops.I can't imagine a problem in your system. It can be put into ponds as it does not affect fish. It can be sprayed on vegetables right up to harvest and is safe to eat. I expect you would put in the same dose as recommended for a pond of the same volume.