I have sprayed "KRYLON" on plastic and PVC parts and let cure for 2 hours and put them in the tank with out any bad effects...
KRYLON is designed to coat plastic, without having to prime first...I think there is more suitable rattle-can paint he could try...
Matter of fact, after thinking about it....try some clear appliance epoxy, let cure like the manufacturer suggest, then test it in a tote of water and see what you think...
c'Mon Bob... to each their own...Some things are very near and dear to people and nobody else... and who cares anyway, it does belong to him after all...
Taste is such personal subject anyway...
Room for all and then some...