As I've said on other posts, I have a large amount of D.E. and use it on and in my goats, dog, cats, cockatiels, chickens, ducks ... I sprinkle it on my carpets to kill bugs and fleas. I take it internally both 'kicked back' [dumped into the water, stirred and drank quickly] and from a jug of 'silica water'.
I will take it always because a constant gentle cleansing out is a good thing! Which reminds me, I need to put some in the animal water buckets to try to kill the algae trying to grow there.
I doubt if it will kill algae. It was once an algae itself. Try a little peroxide in the water instead.