You can but it won't be cycled. The bacteria are different. Once you add enough salt it will kill the FW bacteria and you have to wait for the SW bacteria.
I did it with mine over time because I was bringing a puffer from FW to SW.
No chance I would reuse water from a freshwater tank. Especially in a tank that big since there will undoubtedly be a ton invested in livestock. Water is easily one of the cheapest things in this hobby. I would just do it by the book and start with fresh salt water. It probably wouldn't matter. But just why do it? Play it safe.
Check the tds of your freshwater tanks if it is 0 (which I would be totally amazed) than it would be fine to use if it is anything else then I would make fresh RO/DI saltwater.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.