So a lot of shrimp keepers prepare and cycle a completely new tank when their old active substrate is loosing its properties. But is it really necessary ? Can't you just drain the whole water from the tank, keep your filter media submerged in the drained water, replace the substrate and put everything back in  ? I had to do that with my cull tank - there is inert substrate but it was just too dirty and the nitrates were rising way to quickly. So I just cleaned the substrate under tap w