Genesis once bubbled...
sucks canal water in the salt, especially if there is any stainless steel in contact with it. Like, for instance, the SS hose clamps that connect the tank to it.
It WILL galvanically turn to white DUST.
Stay away from such "solutions" - they are not. In fact, they are dangerous.
For the same reason if you're using a stage bottle rig with a pony make DAMN SURE you run the hose clamp through a piece of vinyl tubing, so that no part of the clamp touches the tank. Having the TANK corrode (and if its aluminum, in salt water, it WILL!) would be VERY bad.
The best solution for a pony is to sling it like a stage bottle, especially if you intend to actually use a decent-sized pony (19cf or bigger.)
If you doing a 6cf then go ahead and mount it somewhere, but make sure you practice your "Hail Mary" - are 100' you'll have about that long before its gone, and it may actually CAUSE an entanglement!