I changed from gravel to eco complete after my tank was up for a month and things went well. No fish died and my plants were O.K. I drained my tank and saved most of the water, carefully removed the gravel and put the substrate and water back in. I'm not sure about the fluorite but the eco only clouded my water for a few hours. I didn't go with fluorite because I read it's messy to work with. The eco complete doesn't cloud the water when you plant plants and clean the bottom etc. I've had it in there for about 8 months now and I am completely satisfied. When you have substrate instead of gravel you don't suck up the bottom with a gravel cleaner either. You just skim the bottom to suck the junk off it, it works well after you get the hang of it. I hope this bit of advice helps.