Well since last time I posted on here I was just getting into fish keeping and only had one tank, this was less that prob 6-8 months ago or even less. Well during the time of my fish keeping I've learned a lot about fish and fish keeping and tricks and things of that sort. Now several months later I know have 4 fish tanks 3 which are freshwater and 1 that is saltwater. I have had nothing but great success with all my tanks during the months and have now even some brackish fish like Rainbow fish and a very nice and fat Green Spotted puffer.. I have had them all now for a little over 2 months now I would say kept in a solid freshwater tanks that I have with just basic aquarium. What I am wanting to know now is I'm wanting to turn one of my tanks into a BRACKISH tank, the tank is fully cycled with nice green alge and has nothing else in now except the green spotted puffer b/c I moved the fish into another tank b/c he's now getting where he likes to nip other fishes fins. The tank I have him in is just purly freshwater with basic aquarium salt and I want to turn it brackish so the green spotted puffer will start to turn into his normal color. But what I need to know is, with the BASIC AQUARIUM SALT in the water will I have to completely start the tank over then at the INSTANT OCEAN salt or would it be fine to mix the 2 together?