On the... plastic grids ... I never used them, more one way to do this... me, I always put my sand in & when wiggled my rock down into it.
DC Runner have also adaptors for flexible tubes and for rigid PVC tubing, but on 25 and 30mm. RS Reefer have 20mm tube. I ordered online some reducer from 25 to 20mm and everything will be just fine.My Quiet one 4000 return pump had these adapters included, Which is what you are looking for. It threads over 1" outlet, and has 20 & 25mm tapered barbs on it.
Part #R440325
http://www.lifegardaquatics.com/product-replacement-part/quiet-one-aquarium-pumps/
My system is still "dry", no water in, but how can you "reset" a mechanical valve??? Is a floating device connected to a valve, actually same concept as on toilets.Hey mate. Had any problems with your ATO stopping? Mine is constantly stopping every couple of days and needs to be reset.