So I've had my 180 set up for over 5 years now and haven't really had the opportunity to mess around with it too much. For the past few months, I've been wanting to change my current substrate, a pretty rough pea gravel over to black fluorite capped with black fluorite sand, but I've struggled to find any similar changes which haven't involved moving fish in and out of the aquarium. For a number of reasons, moving my livestock; a small shoal of rainbow fish and a single tiger plec, is not really feasible, and hence I'm going to need to do the change with the fish in. Initially, I wanted a smaller, finer substrate that would harbour the nutrients that my pea gravel so desperately lacked and enable runners to grow, seemingly unlike the current gravel, hence I thought fluorite would be ideal, given it also didn't give a huge ammonia spike when introduced. However, I've heard about the dustiness of the product, and am also concerned about the bacteria being removed as I remove my current gravel. Having stuck with the internal filter that came with the Juwel, I don't have many bacteria living in my filter, hence I was pretty concerned about new tank syndrome, so I was wondering whether gradual changes in substrate would help this, or whether holding the gravel in 'gravel socks' would also be useful. Ultimately, I'm looking to heavily plant and remain kinda low tech; no injected CO2 but I'll use root tabs and ferts where necessary, but the initial change over from gravel to fluorite is one that concerns me quite a bit. The last thing I want is a bunch of fish deaths I'd really appreciate some advice on how to approach this change, and whether it's feasible or not. Thanks.