If you don't, then my suggestion is, there are lof better places for some "boat bucks".

If you do have a problem, then assuming you don't have a leak, the likely culprits are:

o Hoses (including the waste and vent lines) that pass gas (you can likely check those); or,
o In adequate sized or poorly located vent assemblies; and, possibliy,
o You need to pump more often, regardless of the amount of effluent.

Flushing the tanks with water is a good idea. Un-necessary concentration isn't a good thing. Of course, you don't use chlorine or some other agent?

As Rich points out, the environment in which the aerator pump is operating is not "friendly". However, I would observe that you could replace the little aquarium pump 5-8 times (or whatever) for the cost of the Groco unit. I don't know how quickly the aquarium units would "die"Putting a new fitting in the tank probably has a greater likelihood of leaking with a difficult to seal poly tank. (Remember the expression: "Let no good deed go unpunished.'')