I have a few questions about a cpr backpack i got used. (don't worry the former owner had tube worms which would have been killed if there was copper in the system.) my question is whether the main chamber where the water is expelled and the big pipe is supposed to have anything in it. also, what is the purpose of the grey thing on top of the intake chamber? it has no water in it. is the rubber intake tube supposed to be free floating? theres also a bunch of foamy buildup on the top left over from when i put the sand in the tank, which is still very cloudy after a few hours.