 harmful to mosquito larvae harmless to everything else so you know birds can drink it dogs can drink it horse can drink it you know any kind of container holding water we sell an awful lot to ranchers and farmers they have stock tanks yeah they need to for their livestock to drink and but that's a prime area for mosquitoes so yeah they throw a dunk or a piece of dunk in that every 30 days or so and that keeps the mosquitoes from breeding there