whats the difference between he Recirculating Skimmers and the Needlewheel Skimmers??

whats better and you you have a preference?
i cant decide which one would be better for my 36g....

Well, many recirculating skimers ARE needlewheel skimmers. A needlewheel is a kind of pump (or more propperly, a type of pump impeller). The impeller on a NW pump has protrusions on it, like this one from a Sedra pump.

http://i42.photobucket.com/albums/e332/pearsonhurst/1137.jpg

The small needles on the impeller chop up the air sucked in through the venturi to create very fine bubbles.

A recirculating skimmer has oneor more pumps that pull water (and air) from the bottom of the skimmer and reinject it in the top of the skimmer at a downward or sideways angle to increase the dwell time of the bubbles. This pump is different from the pump that feeds the skimmer.

Take my skimmer for example. It's a Deltec APF600. Water is fed into the skimer by an Aquaclear 30 powerhead, just like you might find in any display tank. Then, mounted to the side of theskimmer is an Aquabee recirculating needlewheel pump. This pump recirculates the water in the skimmer AND injects the air for the bubbes in the skimmer.

http://i42.photobucket.com/albums/e332/pearsonhurst/ap-600.jpg
Pic courtesey o Deltec USA

The feed pump i not pictured here, but you can see the Aquabee an how it's hooked up.

There are some skimmers out there that use a needlewheel pump to feed the skimmer and are not reirculating. In those cases, he water and air mix are fed into the skimmer by a needlewheel pump. Generaly, you get a poorer performance from many of these skimmers because the air and water are fed into the skimmer bu the same pump, and so it can not process as much water, and the dwell time is lower than it would be with a recirculating skimmer.

^^^ what he said ^^^

ok well i like the sound of that thanx PHURST!!
so i dont understand how you would use a powerhead to feed the skimmer if you have an overflow?
how would you have them connected?

Any idea on how much better a Euro-Reef RC-80 (recirculating) performs compared to a RS-80 (non-recirculating)? The price difference is considerable...

There are 2 ways you could go about hooking the skimmer up. The prefered way, would be to have the return water fed directly to the skimmer via gravity. This way, you get nothing but raw tank wayter, plus the gunk that gets skimmed of the top of the water. The other way would be to have your return water flow into your sump as normal, and then have a small powerhead pumping water from the sump into the skimmer.

I'm currently using the powerhead mehod, nut I just picked up a mag 18 last night in anticipation of replumbing everything under the stand, and will be switching over to a gravity feed.


As far as the difference in performance of the Euro-Reef skimmers, I have no hard data, nor have I seen them in action personaly, so I can't say ifthe price difference is worth it, but generaly speaking, recirc skimmers are a good bit more efficient.