Then slowly the holes get plugged (under the media) and they will and KaBOOM !...the whole thing blows up ..... basically.

I used a simple siphon (not simon) when I had media grow beds. 3 pieces of 2" PVC and 2 90 degree elbows. One piece was the stand pipe which fixes the water height, one short piece to connect the elbows together and the last piece elbowed down toward the bottom and just off the bottom to insure a good drain. Takes some experimenting to get it just right, but when you do....it can't be beat....breaks and drains perfect every time.. OH and as Keith_r said... the pump runs continous.