Who rates skimmers

[untamed]

I'm recalling that study that recently tried to measure WHAT was being removed by skimmers and how quickly various models removed it.

I believe that their conclusions were that the "larger" skimmer (the one the processed a larger volume of water per hour) removed the measured stuff more quickly, but that all the skimmers tested reduced the measured stuff to about the same level given time.

It struck me that a big difference between the test environment and an actual aquarium is that the aquarium continually generates new waste so a truly undersized skimmer won't ever get the chance to catch up and waste could accumulate.

Yes, I agree...it is more about bioload than actual water volume.

IMHO, size matters. In order to increase the amount of water it can process per hour, the chamber needs to get bigger. Increasing the flow rate with a smaller chamber just reduces the amount of time the water is in contact with the air bubbles (dwell time). In my case, I wanted to get to 1.5x tank volume per hour (600gph) with 2 minute dwell time inside the skimmer. That means that I need to have a 20 gallon chamber....yikes!

After that, I didn't really pay attention to what the skimmer says it is rated for.

[golf nut]

BK will tell you in a heartbeat that you can overdo skimming by buying a unit that is oversize, it simply doesn't work, or should I say doesn't work properly.

I know there is a distinct difference between having the skimmer in the tank with no sump as compared to having a sump with a 10 times turnover, it just isn't the same, the tank install though ugly will work better every time, explaining it is a different matter.

[Palmer]

Originally Posted by Mr OM

BK will tell you in a heartbeat that you can overdo skimming by buying a unit that is oversize, it simply doesn't work, or should I say doesn't work properly.

I know there is a distinct difference between having the skimmer in the tank with no sump as compared to having a sump with a 10 times turnover, it just isn't the same, the tank install though ugly will work better every time, explaining it is a different matter.

If the tank install works better every time then is it reasonable to assume a hang on the back skimmer on the main tank is also better than an in sump set up?

Palmer

[sphelps]

In sump works better because of the overflow effect. The high specific gravity in salt tanks results in proteins/organics rising. the idea of the sump and overflow system is that the overflow constantly sends the top water from the display to the sump.

[steveg]

Hi there, so you are suggesting that the best way to operate a skimmer is to take water directly from the display tank and return it there instead of doing that from the sump?

Originally Posted by Mr OM

BK will tell you in a heartbeat that you can overdo skimming by buying a unit that is oversize, it simply doesn't work, or should I say doesn't work properly.

I know there is a distinct difference between having the skimmer in the tank with no sump as compared to having a sump with a 10 times turnover, it just isn't the same, the tank install though ugly will work better every time, explaining it is a different matter.

[golf nut]

Originally Posted by steveg

Hi there, so you are suggesting that the best way to operate a skimmer is to take water directly from the display tank and return it there instead of doing that from the sump?

I am suggesting that you have the sump turnover rate at the correct volume to get maximum results from the skimmer, typically this will be a lot less than the previously suggested 10x rate.

[sphelps]

Originally Posted by Mr OM

I am suggesting that you have the sump turnover rate at the correct volume to get maximum results from the skimmer, typically this will be a lot less than the previously suggested 10x rate.

But you can't explain why? Just cause, right?

[Canadian]

This is somewhat dependent on your sump layout but think of this analogy:

If I drop a small piece of sinking pellet food down my overflow and I have one of two options:

a) High flow rate through my sump
b) Low flow rate through my sump

Which one do you think is most likely to allow the intake/suction of the skimmer intake to pull in the piece of food? The one ripping the current past the skimmer or the one slowly plodding along?

I'd certainly rather pull mechanical chunks of organic waste out of my tank before they have a chance to break down and then become part of the chemical soup in the water.

[sphelps]

Originally Posted by Canadian

This is somewhat dependent on your sump layout but think of this analogy:

If I drop a small piece of sinking pellet food down my overflow and I have one of two options:

a) High flow rate through my sump
b) Low flow rate through my sump

Which one do you think is most likely to allow the intake/suction of the skimmer intake to pull in the piece of food? The one ripping the current past the skimmer or the one slowly plodding along?

I'd certainly rather pull mechanical chunks of organic waste out of my tank before they have a chance to break down and then become part of the chemical soup in the water.

While I see your view and get what you're trying to say two problems exist with your example. First a skimmer removes dissolved organics which I guess can be compared with food but we don't place organics/food in our overflow but rather rely on flow to get them there. So in real life that piece of food will get to the overflow faster if flow is higher, resulting in going to the sump sooner. Dissolved organics should be looked at differently than a food pellet, its concentration is distributed throughout the tank not in one particular location.

The second problem is the assumption less flow through the sump results in more water being filtered though the skimmer before going back to the display. First these are independent, the skimmer outputs the same as it takes in. So exactly how could one possibly determine how much overflow water is actually going in the skimmer and not simply bypassing it completely? With a lower turnover the amount of water being constantly recycled through the skimmer could actually be higher meaning less overflow water is going in compared to high turnover.

Regardless the point I'm making is that the two are completely independent. Dissolved organics are dissolved meaning the concentration throughout the tank will be virtually constant. The amount of organics taken in by a skimmer is essentially constant and independent from the water flow moving past it. High or low turnover (in limits), a standard in sump skimmer will work the same.

Lower sump flow rates are related to lower noise and less air bubbles but not skimmer performance. The only reading I've seen relating these two suggest higher flow rates as it will "keep solids in suspension, which increases feeding opportunities by fishes and invertebrates, and improves filter/skimmer opportunities to export such matter in a well-designed system"

[robert]

Brad - I like your theory, it makes sense to me. I have a question though. Which of those 2 parameters is more tweak-able/forgiving - tank volume per hour or dwell time?

For example, I have ASM 5G with about 6gal cylinder capacity. Manufacturer suggested system size for this one is 700gal. Granted, real life users would not put this skimmer on anything bigger than 350-375gal. Now, applying your theory, keeping flow at 1.5x volume of the tank with 2 min. dwell time this skimmer is no good for anything bigger than 120gal. Which parameter would you tweak for bigger system? Volume per hour or dwell time? No, "Get a bigger skimmer" is not applicable answer at this time.

Thanks a lot.

Cheers.

Originally Posted by untamed

I'm recalling that study that recently tried to measure WHAT was being removed by skimmers and how quickly various models removed it.

I believe that their conclusions were that the "larger" skimmer (the one the processed a larger volume of water per hour) removed the measured stuff more quickly, but that all the skimmers tested reduced the measured stuff to about the same level given time.

It struck me that a big difference between the test environment and an actual aquarium is that the aquarium continually generates new waste so a truly undersized skimmer won't ever get the chance to catch up and waste could accumulate.

Yes, I agree...it is more about bioload than actual water volume.

IMHO, size matters. In order to increase the amount of water it can process per hour, the chamber needs to get bigger. Increasing the flow rate with a smaller chamber just reduces the amount of time the water is in contact with the air bubbles (dwell time). In my case, I wanted to get to 1.5x tank volume per hour (600gph) with 2 minute dwell time inside the skimmer. That means that I need to have a 20 gallon chamber....yikes!

After that, I didn't really pay attention to what the skimmer says it is rated for.