There's only one type of aeration system
An air pump outside the tank and piping inside the tank--both of sufficient size and design to oxygenate the entire contents of the tank. Go to the Groco website (link below) and take a look at their "Sweetank" system. Especially look at the schematics for the piping inside the tank. I think most of your questions about how any aerator has to be installed if it's gonna work will be answered.However, IMO aeration only makes sense if you're in "no discharge" waters (99% of which are RI, several places in MA, the Great Lakes, and non-navigable inland lakes) where treatment devices aren't legal, or your boat is too small to have the power resources to support a treatment device...so boats have to have holding tanks big enough to be worth aerating. But in all other waters the use of treatment device means the holding tank is used so seldom, and for such a short time that it's not only not worth the effort, it prob'ly wouldn't be very effective because the aerator wouldn't run enough to accomplish anything.