From salt to fresh to salt

[Synergy]

My brother aquired a previously used saltwater tank, he wants to set it up as salt but doesnt have the cash right now to do it. It still has the cc substrate that was used for the saltwater setup . He wants to set it up with the cc substrate and have freshwater fish in the tank then when he has enough money, take the fish and freshwater decorations out, leave the same substrate, empty and clean the tank, then go with saltwater again. Do you see any problems with that if he doesnt use any copper based medications during the frshwater setup? Any special concerns with doing that?

Thanks,
Chris

[Nuhtty]

Personally I wouldnt do it because there are many microorganisms that can live in the substrate and when you switch from FW to SW or SW to FW, those microorganisms will die, causing a huge ammonia spike in the tank.

Not only that, there are other microorganisms that can even survive the transition and possibly introduce disease to the new inhabitants.

Better off emptying, cleaning and starting new.