Thinking of setting up a nano using some of the rock I took out of my last set up, it been in a bucket for two years in the garage, How long should I soak it for and how often should I change the water?
Hard to say, it depends on how clean the rock was when you removed it, I would soak it in RO for a week then change 100% of the water and soak it for another week and test for ammonia nitrate and phosphate, depending on the results either do it again until tests are good, then soak it in circulating salted water until you need it.