Cavitation problem solved!
I disconnected the Danner Mag 9.5, trying to rotate it 90 degrees. I disconnecte the pump (thank God I installed unions!!) and then found that the 90 degree elbow to the intake had a bunch of PVC cement bleeding into the pipe blocking nearly half the intake. No wonder I had cavitation issues. Then, when I reinstalled I managed to crack the pump cover because I used too much teflon tape..... Ugh.
Not wanting to wait days for replacement parts, I figured I might as well put the Eheim Compact+ 3000 to use. Fortunately I had ordered a bunch of 3/4" PVC to barb connectors from FlexPVC.com, so I could make a quick setup with Vinyl tubing like this:
I had no idea the difference it would make. This solution is whisper quiet and it has no problem whatsoever dealing with the full ~800gph (turning tank over more than 5 times per hour). I think I'll leave this solution in place, though I will shorten the PVC as much as I can.
Lessons learned from this:
- Make sure you have plenty of replacement parts and hard to find PVC parts such as Slip-Barb connectors. You never know when you might need them.
- PVC unions are absolutely required. Make sure you put them after/under the ball valve, so you can close the valve, then open the union and not drain your entire tank in the process.
- Leave it to 'ze Germans' to design a qood quality pump.
And finally another gratuitous tank shot (by day this time). This shows the added live rock that is seeding the tank.
PS. Another (unrelated) lesson learned:
- Calibrate your measuring tools. I found out my refractometer was off by almost 0.1!.. and no, it did not forget a zero.