I think so three, but the comment was " RO can't be used in salt water? LMAO!" Indeed, RO cannot be used in salt water. It can be used to purify fresh water for purposes of mixing artificial salts, but that is another thing altogether, and not 'semantics'. If the writer(s) meant RO water can (and usually is) used in the marine aquarium hobby to mix with salts, that is what should be said. The fact is RO cannot be used in salt water, plain and simple. Mere semantics is not the same as the omission of words that change the entire meaning. One can complain 'but you know what I mean', but if that's what you mean, say it. Not something with a different meaning, expecting that others will clean up your sloppy language and read your mind. And, a RO unit can be connected to any pump you want, as long as there is adequate pressure. It's a big world out there, and many ro units are connected to pressure pumps, not faucets. Nobody with a brain would use RO in Salt water, but that is what you wrote. in any case, the issue was mercury, and I stand by my original statements, without reservation.
Speaking of prime, I once nursed a SW fish several inches long back from Venezuela in about a litre of water, with stops a total of three days. Water changes were not possible. Prime, repeatedly administered in small doses did the trick.
