If this is a bilge mounted application, you really have to consider an 'explosion proof' / TENV motor, even with 12vdc.

Also the H2S and various sulfurous compounds in the tank are going to play hell on the pump even when the pump is on; and, as a 'transport phenomenon' such 'acidic' gases will be traveling 'retrograde' in the hosing during pumping / air injection; worse when the pump is off. One would expect Groco to have this all 'worked out' for compatible materials and explosion 'proofness', for that 'price'.