When water sits in a hose, chemicals leach out of the plastic into the water, and it will foam up like you are seeing. Most hoses are labeled with a warning not to drink from them. I let the water run until all the bad stinky stuff is gone (I can smell it), then I fill the waterers. It shouldn't foam then.I would bring it in and flush it really good with hot water. Mine Looks like soap a lot but its from the water hose. Not sure what causes that.
Rabbit poop doesn't have to be composted (rotted/broken down) and can be put straight into the soil around plants without harming them. Most other manure is considered "hot" and will burn plants/roots if it's not composted first.I actually read a little about this before. Dont quote me but I think rabbit poo dont have an odor and chicken has to be sterilized . Maybe rabbit too ? I have seen very small packages of chicken poop for sale before. It was pricey. LOL