I have seen 2 stroke water pumps for $299 which could be great for this type of thing. I saw it in a lawn mower shop in Hamilton.
Don't know about the salt water though but a good rinse would help.
My new tank & sump is 900l, lots of $$$$$ with ASW so a pump would pay its self off rather quickly.
The ASW I use is $129 for 750L.
This type of talk sells things to my wife, her eyes roll around and she lets out a low moan (don't hear that any where else) which means OK (really means do what you want but if we end up in the poor house its my fault)