just browsing today, in response to your suggestion. Here is what actually happened.. I drilled the backhalf 2x3 bar and put the vent into it. I siliconed the hole tight. What was happening is the 2x3 tube was welded 100pct tight on both ends therefore creating a vacuum. Tank would suck until there was no air left in the backhalf bar.I ended up drilling a 1" hole in the bottom of the tube and problem solved. So your theory sent me in the right direction and for that i say thanks