Thanks for the replies. I haven't thought about simple green.
I use bleach. Is the septic tank the same as the one your house is using? If so does anybody in your household use bleach in the wash, toilets?
No...I installed a seperate system just for the kennels. Lots of poop going in this thing, and I don't want to risk upsetting the process if possible. So far, it's working great.