Update time.
We swapped out the Dart with our old 4300 SW (from Sequence). It is louder, due in part to a bad/worn bearing I think, but it pumps alot more water through the tank. So much so that I had to open the gate valve on the skimmer almost all the way and also was able to adjust the Vortecs speed up to just less than 100%. We had them throttled back to 75% or so due to their pulling vortex from the surface at full speed, so I backed each one down to just before they pulled the vortex. The higher water flow raised the in-tank water level to the point where I could turn the Vortecs back up to full speed (2 are at full speed, the other 2 are just below at about 95%). All in all the tank inhabitants seem to be happy with the increased flow (from both the return pump and Vortecs). The fish can be seen out playing in the flow from the Vortecs now, something I had not noticed before.
The one downside to it all is something that I still don't fully understand. When I turned up the return pump output (by swapping it with a stronger pump) and opened the gate valve on the skimmer drain pipe I could not return to the balance I had previously between the water level in the skimmer and the water level in the overflow boxes. The water level in the overflows rose significantly but the level in the skimmer dropped to the point where it was only half way up the riser cone (before I had it tuned to just below the twistlock collar). What I experienced before was when I closed the gate valve it would raise the level in both the skimmer and overflows. I adjusted the return pump output to the point where the overflows are at the point where any higher would be a concern (and I wanted to leave some room for "just in case" IE: a snail gets in and reduces the pipe/drain capacity, etc). The restriction is in the 2" drain at this point, not in the overflow teeth.
I ran a few tests to see how the different settings affected the skimmer production and tank overall appearance. For each test I letit run for 12+ hours with the skimmer collection cup drain valve closed, so that I could see the level and "density" of skimmate produced.
Return pump medium, gate valve partially closed, skimmer level medium
The skimmate production density stayed the same, dark green-tea colored, watery skimmate. The amount was about the same as we had before with the old Dart pump and the gate valve closed.
With the Dart we had the gate valve closed to about 50% or less (6 - 7 full turns of the gate valve handle). That seemed like a huge waste to me, which was why we decided to change back to the stronger pump.
Return pump high, gate valve open, skimmer level low
Produced alot more skimmate than I had expected, and the skimmate was alot wetter than I would have thought. It appeared that the amount was a 50%+ increase from previous settings and the skimmate was "watery", bascially the same as before. This surprised me since the level in the skimmer was only half way up the cone with the recirc and air pump running (which both push the water levels up).
I can only speculate that the increased water flow through the skimmer countered the negative impact of having the water level so low within the skimmer. This is how we are currently running our tank.
Any thoughts or suggestions ?
