Per the product manufacturer of the BTI Mosquito Dunks the insecticidal toxins are a by-product of the bacillius thuringiensis in the dunks with is not harmful in any way to non-target animals.
Each brisket of BTI Mosquito Dunks treats 100 square feet so one dunk will be sufficient for a bird bath.
Yes the BTI Mosquito Dunks can be tied to a grill in a storm drain to prevent it moving. Be sure it is done so in a way that it will contact water when built up and not the ground.
Herbicides such as should not effect the BTI Mosquito Dunks as long as it is used as directed. We wouldn't recommend spraying the dunks directly though just to be on the safe side but if applied to a body of water that is also treated with an aquatic herbicide, the dunks would not be effected.
BTI Mosquito Dunks are safe for birdbaths, old automobile tires, rain barrels, abandoned or unused swimming pools (particularly above ground types), tree holes, roof gutters for collecting rainwater, flower pots, animal watering troughs, elevator shafts, basements that flood, sump pumps and any drainage areas within buildings. One briquet treats up tp 100 sq ft of water.
