Join Date: Jan 2018
Location: Chicago NW burbs
My 125gallon is ecocomplete covered with playsand, started almost 4 years ago.
Couple of observations:
Slope - sand will slide whenever it wants to slide no matter the slope just from the flows of filters (my flow is not crazy and not high at all). I have a ridge in the middle. Hardscape will affect flow and floor shape too. So don't count on it.
Gasses - another vote for "not much of a concern". IMO raking or no raking will have exactly same level of impact - none. MTS will steer it good.
Appearance - After years I do have some black susbstrate particles emerge (this happens when pulling plant roots), but it is still almost all sand on top. And that's with the ever changing "flow" of the sand dunes. So yes, the substrate will mostly stay down without sand seeping.
Overall I really like my substrate choice. And my cories like it too. It's amazing to watch them sifting for live worms that I deposit into the sand.