[sphelps]

Originally Posted by mr.wilson

I stated there was no head loss, not that there was no friction loss. I was responding to your comment about head loss with closed loop pumps being significant. If you use the RC flow calculator you will see that an elbow, two ball valves and 15' of pipe will drop a Blueline 70 from 1710 GPH to 1620 GPH. This is an example of a closed loop pump located in a basement below the tank, you would have less friction if it were located directly below the tank and of course you could add friction with other plumbing. I simply don't see this as a significant issue, and you never mentioned it in your comparison for likely the same reason.

Yes very good but that's over 8 feet of head pressure, it's significant but its a pressure rated pump so flow losses are minimal with added pressure. How much power is that using? Around 300W, ouch! not something I would want to run. And exactly who can plumb a closed loop with such little fittings? Take the same case but more realistic and add 3 more elbows, 4 more ball valves, 6 unions, over 4 exists and you'll see that jump up to 13 feet. Then compare that to a more common pump like a dart and you'll get just over 10 feet which drops the flow from 3600 to 1200. You did state that friction exists but it was small, this simply isn't true and there would be a huge difference in plumbing to the basement, add 20 more feet of pipe and pressure jumps to 16.5 feet on the blueline. And none of that even considers what that OM does for head loss, I wouldn't even want to know.

What are you trying to accomplish with variable speed on the Vortechs or Streams? An intermittent reduction in output only reduces the volume of water you are moving (and electrical consumption). An Oceansmotions 4 Way maintains the same flow rate within the tank while offering a passive surge and allows detritus to momentarily settle for coral feeding, then pick up again before it reaches the substrate. If you time the ports properly, detritus can be passed from one end of the tank to the other using 50% less flow than four static effluents. A powerhead system is limited to side to side flow, and while one side is off, your flow is now at 50% capacity. A closed loop pump with a 4 way is always delivering the right amount of water to right location at all times. You would need twice as many powerheads to make up for the time they are not running for side to side motion.

You're obviously not too familiar with what my profilux controller can do with my Tunzes, way beyond side to side movement and simple pulses. From sine waves to right angle shorts and random % additions plus storm simulations natural wave movements and night modes I'm sorry but it does way more good than a OM. You could do the exact same as an OM with such power heads at that would be the simplest program, but nobody would because the other options are better.

What are the solutions that they offer. The Dana Riddle article confirmed some of the flow claims so they got some points with me for that, and I would be happy to hear about more hidden benefits.

Check out that nice picture I already posted, rock covers can hide such power heads just like a closed loop.

Shaft driven pumps like Sequence are not suitable for marine aquariums so I'm not surprised you had problems, but that is like me directly comparing a maxijet to a Vortech, which I have not. The main problem hobbyists experience with external pumps is sumps running dry (which would also happen with a submersible pump), and saltwater dripping on the motor (which is negligence). To a lesser extent sand in the impeller or dust in the fan also occur, but once again these same people would be negligent with powerheads. I have experienced a 1% return or repair issue with external pumps, and although I don't use powerheads, I always see a mountain of them at local aquarium stores return bins and replacement parts are well stocked, while replacement parts for external pumps is a non-issue.

All the external pumps who have recommended are shaft drive, aren't they? I used darts as an example because you mentioned them in a previous post.

Sequence makes a DC Dart. The only application I could see is a series of deep charge marine batteries for a backup system but personally I prefer air lifts.

Good stuff, so no comebacks for CLs