If you put it in the water, it will sink to the bottom. They'll get the silica which is great, but for parasites and worms, you need to add it to their food somehow.
I also use it on their fur or feathers [I have goats and chickens and ducks and geese and cats!] by just dusting it onto them, trying very hard not to breathe the fine dust.
I also put it in the stalls, sheds and such where the animals stay to reduce flies and other pests. This also works around plants, trees, gardens, etc.
I also take the D.E. myself for the silica and for the parasite and general internal cleansing.
Now if I could find something to keep the algae from forming in the water tubs and duck ponds!!!