I have about 100 lbs. of old southdown sand that I had in a old DSB set-up! I placed all the old SD in a spare 35 gal tank with just a small canister filter & kept the SG around 1.021 just to keep things alive! Anyway I don’t plan to re-use the SD for any more of my saltwater tanks. However I’m thinking of setting up a freshwater planted tank, Can the SD be reused for a planted tank? And will any of the bacteria survive a slow switch from SW to FW?