Cycling

[sswm]

I want to convert my freshwater tank to a FO saltwater to start off with, will add live rock later. Would the conversion to saltwater kill the mature media in my filter and start my cycle all over again?

 

[SkiFletch]

Yes, two different species of bacteria here and neither can survive in the salt content (or lack thereof) that the other thrives in. If you do want to do FO, you can fishless cycle the tank the same way as normal. I'd suggest though picking up a little piece of rubble for a few bucks and sticking it in your filter to jumpstart your cycle. Will make things take a week or so as opposed to a whole month