Thanks, the background acts like a BIG overflow box since the water level is slightly below the BG. I made 4 holes in the front, positioned in different areas of the back ground. The picture below will give you an idea on where I positioned them. It's the yellow highlighted area. It creates a pretty strong vacuum that sucks any free floating debris or waste. The bottom and sides of the background is well silicone so all the vacuum pressure is created through the holes I drilled.
As for the sand, I don't vacuum as it's not a very thick layer that my GEOS can't shift for me. As they shift through the sand they release and build up any gas pockets or debris or waste embedded in the sand. Reason for the Geo's in my tank. My sand never looks the same as hills and pot holes are created often by my Geos.
The filtration I have is an FX5 and Eheim. I want to incorporate a wet & dry as well, just haven't had the time to do so.
Hopefully I answered your question. thanks...