Partially replacing old Eco Complete with sand, partial teardown
I've had a 20g long running since 2012 and lately I've been thinking of replacing the (long-since depleted) eco complete with black sand. There's mainly water column feeders in the tank now, so there's not much point in putting in more of another fertilized substrate. I'd love to give cories a go in this tank, so switching to sand seems like the natural choice.
Since the eco complete has sort of separated itself into finer particles at the bottom and chunkier bits at the top, I was hoping it would be possible to remove and replace only the top layer. I'd like to avoid completely tearing the tank down if possible, and just do maybe half or a third at a time.
The question is... is there any reason I shouldn't do this? Both for the partial replacement and partial teardown. Thanks!