Who rates skimmers

[Canadian]

Originally Posted by mr.wilson

They do use less power than any closed loop pump currently on the market, but the flow rates they have been designated are not the true values of the water they move.

Absolutely not true. In fact one of the pumps was recently scruitinized by Dana Riddle and found to move MORE water than the manufacturers claims:
http://www.advancedaquarist.com/2009/10/review

Most of the closed loop effluents I use point up from the bottom to keep detritus suspended and to move dead water from lower regions to the air/water interface at the surface for gas exchange (oxygenation). Vortechs are only suitable for end to end flow, and they do it well.

Again, not true. The pickup from my little Vortech MP20 draws detritus up from the bottom of the tank 14" beneath it to keep it suspended in the water column

Closed loop pumps draw in as much water as they put out. So do Vortechs, but the water intake doesn't have any impact on flow dynamics and flow is more turbulent (pumping into walls, rocks & opposing flow) than laminar (circular or rolling effect) without losing velocity due to friction or diffusion.

See above - not true.

Typical powerhead set-ups direct water at the reef structure. This is not how it works on natural reefs. Water should change direction to offer suspended food from all angles. Good flow creates a snow globe effect. Chaotic flow with poorly placed powerheads drives detritus into reef structures and the sand bed.

Strawman argument. Poorly directed and placed closed loop outlets do likewise. Your argument here is simply a function of poor application and has absolutely nothing to do with the inherent qualities of either a prop pump or closed loop.

A Sequence Dart pump uses 135 watts, and I pay $0.11 per Kw/h in Toronto including all of the extraneous charges. That comes to less than $11 per month if it runs 24hrs a day. If you can find a more efficient pump that truly moves the same amount of water (3600GPH) at half the wattage then you save $5.50 per month. A savings is a savings, but $5.00 isn't enough to tip the scale much.

And that 100+ watts difference in heat produced is pumped back into the room and eventually requires more hydro consumption in the form of increased work for the chiller, AC, fan to remove to keep temperatures down. Now you've probably doubled your savings to around $120 a year - I'll take that $120 in savings and go buy some pretty new frags.

They also require regular cleaning that you don't need with closed loop systems.

Just like you have to clean the impeller on a closed loop pump to remove eventual precipitation so too do you clean up the propeller on a prop pump - no difference in maintenance here.

[golf nut]

We are not really talking apples to apples here, both vortech and tunze claim flow numbers that becomes converted to gallons per hour of flow.
I would not argue their claims in the slightest, but just for a second could you answer me one simple question, if a vortech or tunze produce 3000- gph of flow , and you throttle back a dart to produce 3000 gph would the result be the same?

[sphelps]

Originally Posted by Mr OM

We are not really talking apples to apples here, both vortech and tunze claim flow numbers that becomes converted to gallons per hour of flow.
I would not argue their claims in the slightest, but just for a second could you answer me one simple question, if a vortech or tunze produce 3000- gph of flow , and you throttle back a dart to produce 3000 gph would the result be the same?

Tunzes and Vortecs push flow outwards in an expanding direction, this results in a larger area and therefore a lower velocity. Velocity is not that same as flow rate.

[golf nut]

Originally Posted by sphelps

Tunzes and Vortecs push flow outwards in an expanding direction, this results in a larger area and therefore a lower velocity. Velocity is not that same as flow rate.

That wasn't what I asked, so I will rephrase, if I throttle back a Dart to 3000 gph and make the outputs disperse similar to a tunze or vortech would they be similar?

[sphelps]

Originally Posted by Mr OM

That wasn't what I asked, so I will rephrase, if I throttle back a Dart to 3000 gph and make the outputs disperse similar to a tunze or vortech would they be similar?

Yes and no, same flow rate different velocity. The lower velocity and greater spread creates an advantage as simulates natural water movement better.

[golf nut]

So we agree that if I could make the outlets of a Dart replicate the Tunze/vortech with the dart throttled to be the same as the flow then we would have identical flow?

[golf nut]

Originally Posted by sphelps

Yes and no, same flow rate different velocity. The lower velocity and greater spread creates an advantage as simulates natural water movement better.

So we agree that if I could make the outlets of a Dart replicate the Tunze/vortech with the dart throttled to be the same as the flow from the vortech/tunze then we would have identical flow?

[sphelps]

Originally Posted by Mr OM

So we agree that if I could make the outlets of a Dart replicate the Tunze/vortech with the dart throttled to be the same as the flow from the vortech/tunze then we would have identical flow?

well not quite. A propeller pushes flow outward so it would take more than simply matching nozzle size, you would need some kind of special adapter on the dart outlet to produce the same results, but if that was the case yes I believe the results would be identical. Other than one uses 15W and the other uses 150W.

Seems strange you want to confirm this so badly, do you have a point you plan on springing on me once I agreed?

[mr.wilson]

Originally Posted by sphelps

Tunzes and Vortecs push flow outwards in an expanding direction, this results in a larger area and therefore a lower velocity. Velocity is not that same as flow rate.

It also results in detritus being pushed down into the substrate rather than up to the surface for suspension, surface skimming and gas exchange.

If you like the outward flow of a Vortech, it can be easily replicated on a closed loop with a penductor, or a series of them if you split your closed loop into several ports.

[littlesilvermax]

Originally Posted by Mr OM

We are not really talking apples to apples here, both vortech and tunze claim flow numbers that becomes converted to gallons per hour of flow.
I would not argue their claims in the slightest, but just for a second could you answer me one simple question, if a vortech or tunze produce 3000- gph of flow , and you throttle back a dart to produce 3000 gph would the result be the same?

I know what you are saying, and totally agree.

3000 gph from a dart will INDUCE a lot more flow then that in the tank. it is hard to compare that with a tunze or similar powerhead.