I think it's the low demand for such pumps. While I'm sure your local distributor can't keep Red Dragon pumps in stock, it's still a tiny market compared to the industrial pumps we currently use in the hobby.

True but I believe it's a small market because prices are high not the opposite, just like any other high end product. It's certainly not for everybody, people have to make their own decisions which products will best fit their needs.

Mr. Wilson got me curious when he mentioned the temperature his pump ran at so I checked mine tonight.

http://i11.photobucket.com/albums/a1...ps/photo-2.jpg

It's the RD 6.5m3, hottest part was at the top back corner, was around 92F but dropped to 90.8F when I snapped the shot.

I guess that puts your turnover rate at about 15x with the head loss :wink:

I believe it's actually just over 10x

Here's the pump curve for the RD 6.5m3 and 8.5m3, some people have asked me about it. Sorry but you'll have to convert :razz:

http://english.royal-exclusiv.de/Mee...um/lkurve6.gif

http://english.royal-exclusiv.de/Mee...um/lkurve8.gif

I have to disagree, Red Dragon pumps are far superior to Eheim. If you have the money for a Red Dragon then buy one, you wont be disappointed. That said, poseidon makes a very quiet pump also, but you are limited to lower flow rates and massive amounts of heat transfer.

Mind the motor housing surface temperature is deceiving. It's definitely not the best indication of heat transfer to the tank water. The anti-calcium loop (ie. water jacket) provides active cooling for the motor by transferring the heat directly to fluid.

I've never owned a Red Dragon pump, nor do I appreciate the price, but it's nice to see a little more rigor applied to the design of hobby pumps. That said the mystique behind them is a bit much for my tastes. There are certain realities that need to be accepted as to the maximum efficiency of an electric motor, or its heat output. It's not an especially detailed set of calculations...

My recommendation for a quiet return pump? Buy a recommended and medium priced pump, create a damping base and decouple the discharge from the return piping with some form of expansion joint.

The Poseidon/Velocity pump has a very hot external temperature, but this because the heat is on the outside, not the inside. Poseidon proved to have less heat transfer than Iwaki during testing. The heat transfer for a 50 gallon tank was not measurable. A heat sink would be a good addition to the Poseidon nonetheless. I like that it doesn't have a fan, nor do I think it needs it.

The older Red Dragon pumps have poor head pressure. Losing more than 1/3 of the flow with modest head pressure is disappointing for that kind of money. I don't now much about the new line of Red Dragon pumps, but I would consider using them if they were good quality even if they are expensive. For me it's more of a value for money issue than actual cost.