needlewheel vs. venturi

[donman]

Can someone please tell me what the big differences are between these two types of skimmers? I have used both, to complete satisfaction, but really, what is the deal, newer technology = better skimmers? Is that really all it boils down to?

[Rgwiz11]

My understanding is that they are basically the same thing and work on the same principal. That is, water + air get pumped into the skimmer, a whirlpool is created and bubbles come out in the collection cup. The only thing different is that in a needle wheel skimmer, there is a propeller that spins around and agitates the incoming water+air mixture even further and is supposed to create even finer bubbles.

Personally, I use the RemoraPro. It's different being that it does not involve a vortex being created. It shoots a jet of water at high pressure down into a standing pool which creates the contact bubbles needed for skimming. The drawback is that they are a bit noisier, but in my limited experience, they do a lot better job skimming.

[donman]

thanks RGwiz, any other opinions on this matter?

[John Simon]

Personally I use a AquaC EV-240 which is spray injection like the RemoraPro. I prefer it since there is no Venturi to get clogged. So the only maintence is to empty and clean the skimmer cup.

Here is a good description of the two and the differences from Suite 101 (which seems to be down so the link is to the Google cache of the site):

Venturi and Needle Wheel Skimmers: Two of the Most Popular Skimming Technologies Explained | Suite101.com

Venturi Driven Protein Skimmers

Venturi driven protein skimmers inject small air bubbles into the skimmer chamber through the venture valve. These bubbles create a sort of whirlpool effect in the chamber, which increases contact time. Venturi driven skimmers don't require a separate air pump since the venture valve is responsible for injecting the bubbles. The downside here is that venturi skimmers need high pressure, dedicated pumps (usually powerheads when used in-sump) that can deal with back pressure in order to function well. Some Venturi driven skimmers come with pumps, others don't. Even the ones which are sold with pumps are sometimes paired with pumps that are not powerful enough to make the skimmer run at maximum efficiency—always check with the manufacturer. Also take into account the heat the pump will add to the system. You will need to clean the venturi valve from time to time by reaming it, but other than that, they are pretty maintenance free.

Needle-Wheel Skimmers

Most needle wheel protein skimmers are just venturi skimmers with a so-called "needle wheel" impeller. A venturi valve is still used to inject the air—the difference is that the water is then drawn through the needle wheel impeller, which chops the incoming bubbles into a fine mist. "These needle-wheel impellers can really hack bubbles apart," says Kim, "which is great since small bubbles are ideal for efficient skimming. The better needle-wheel skimmers on the market are notorious for building a dense, milky froth. This makes for efficient skimming in a relatively compact package." The needle wheel skimmer's efficiency is largely responsible for its huge popularity. Given that this pump is really a venturi hybrid, it has the same downsides as those listed above for venture driven skimmers. Kim also cautions against needle wheel skimmers' low rate of air and water flow. "A needle-wheel impeller is designed to chop up air bubbles, and it doesn't do a very good job at moving water flow," Kim says. "Venturi and spray-injection skimmers driven by pumps with normal impellers move a lot more water flow. That offers some advantages, especially on large tanks."

Edited December 7, 2009 by John Simon

[donman]

thanks John