Hmm. never heard of that before, but I've talked to a person who specializes in brackish fish and he said it's best to keep them in brackish water, they will be happier and live longer since most FW species are very rare. I know this because I bought one before and researched it, they are very difficult to feed though and I would only recommend them in species tanks. I may be wrong aobut the fw and sw type but never heard of that before, none of the resources i've read has said that, neither have they said that they should be kept in straight saltwater. But then again I guess they could all be wrong
