Beckett vs. Needlewheel skimmers

[Roland Jacques]

I think you need to understand this for the rest to make sence. The Bubble dwell time is no different in a recirc NW skimmer than a insump NW skimmer.

Thier may be slight vareiances maybe 2%-3%. More than not in the bubble dwell would be in favor of the in sump model. (in you tipical skimmer) not the recirc. So rule that out as contributing to the recircs better performace.

 

[Pyrrhus]

With a recirc skimmer you can indeed increase the bubble dwell time. All you need to do is restrict the air intake on the recirc pump. Less air flow=more water flow, which leads to greater entrainment of the bubbles in the water column leading to a longer bubble dwell time.

 

[hahnmeister]

<a href=showthread.php?s=&postid=8363465#post8363465 target=_blank>Originally posted</a> by Roland Jacques
I think you need to understand this for the rest to make sence. The Bubble dwell time is no different in a recirc NW skimmer than a insump NW skimmer.

Thier may be slight vareiances maybe 2%-3%. More than not in the bubble dwell would be in favor of the in sump model. (in you tipical skimmer) not the recirc. So rule that out as contributing to the recircs better performace.

Right, the dwell time, as in the time it takes for a single bubble to rise from the bottom to the top, isnt changed much (although a recirc is a downdraft, so technically, the bubble does take longer to rise), the overall contact time is. The throughput on a recirc skimmer is often 1/4 or less what the throughput might be of a single-pass skimmer... so thats a 4x contact time. Thats what Im saying... that perhaps contact time can make up for less dwell time... or that perhaps a really thick foam head at the top can extend the dwell time, since the bubbles can stay there in suspension for a much longer time than they were on the way there.

And thats what I wonder... did Escobal and all these other skimmer people define what dwell time is in relation to contact time?

 

[alwest45]

<a href=showthread.php?s=&postid=8365178#post8365178 target=_blank>Originally posted</a> by hahnmeister
Right, the dwell time, as in the time it takes for a single bubble to rise from the bottom to the top, isnt changed much (although a recirc is a downdraft, so technically, the bubble does take longer to rise), the overall contact time is. The throughput on a recirc skimmer is often 1/4 or less what the throughput might be of a single-pass skimmer... so thats a 4x contact time. Thats what Im saying... that perhaps contact time can make up for less dwell time... or that perhaps a really thick foam head at the top can extend the dwell time, since the bubbles can stay there in suspension for a much longer time than they were on the way there.

And thats what I wonder... did Escobal and all these other skimmer people define what dwell time is in relation to contact time?

Hahn, when you say a recirc skimmer has maybe 4x the contact time of a non-recirc skimmer (same body/design/size) are you talking about (A) bubble contact time or (B) water contact time. If A, then I don't see it. Other than the small percentage gain you get from the downdraft action of the recirc skimmer it seems the contact time is the same since the bubble still has the same distance to rise. If you mean B, how does it matter whether the water in the skimmer body is mostly "the same" water that was there 30 seconds ago or if it has been swapped out with "new" water from the tank?

Btw, I like your foam theory. I've not heard it before but it does explain a lot of things that were hard to understand. But it does seem to imply that it is relatively easy for a molecule (even one of those elusive "stubborn" molecules) to latch on to a bubble so that it can jouney up to the foam head - it's just that the "stubborn" molecules need more time to get attached enough so they don't detach before the foam exits the skimmer. If correct, isn't this a fairly radical new theory on skimming?

Roland, when you say "The Bubble dwell time is no different in a recirc NW skimmer than a insump NW skimmer" I understand your point. However, it seems to me that most of the other folks talking about needlewheel skimmers don't seem to agree. It seems like they attribute the superior performance of recirc needlewheels (over non-recirc needlewheels) to longer bubble dwell time "since the water recirculates inside the skimmer body". But as you point out, that doesn't seem to be true. But if you are correct (and I believe you), then how to account for superior performance of recirc NW skimmers other than re-exposing partially skimmed water to another wave of bubbles somehow works better than exposing unskimmed (i.e. dirtier) water to the same number of bubbles. How can that be. Or am I somehow missing the explaination for why recirc NW skimmers seem to work better than non-recirc NWs?

Could it be that recirc needlewheel skimmers are the latest versions from the skimmer vendors and as the latest versions they have other engineering tweaks intended to improve their performance which collectively are what's responsible for the perceived improvement of recirc NWs vs. the old-style NWs?

Hey Fudge, what vendor makes your quad-beckett skimmer? What pumps are driving it? Are you getting 180 scfh through it now? It sounds like a good setup for your large SPS tank. Why do you want to change?


Al

 

[alwest45]

<a href=showthread.php?s=&postid=8364278#post8364278 target=_blank>Originally posted</a> by pyrrhus
With a recirc skimmer you can indeed increase the bubble dwell time. All you need to do is restrict the air intake on the recirc pump. Less air flow=more water flow, which leads to greater entrainment of the bubbles in the water column leading to a longer bubble dwell time.

Boy, this seems counterintuitive to me but maybe I misunderstand. Are you saying that decreasing the scfh of the skimmer would increase the bubble dwell time because you would have a stronger countercurrent downflow in the skimmer body due to the larger amount of water (less air means more water in this zero sum game)? But don't you want to increase the aggregrate bubble dwell time and to do that you need more bubbles. It may not matter what a single bubble does or what it's dwell time is. Isn't what really matters some kind of product of the average bubble dwell time times the number of bubbles in the skimmer (minus those that are destroyed)? To improve this it seems like you need more air going through the skimmer. Isn't one of the major goals of skimmer design to improve (increase) the scfh while not increasing the bubble size or turbulence? Won't that approach lead to better skimming?

 

[Roland Jacques]

Al, spent some time with Andy & Tim today over at My Reef Creations. They where setting up thier new recirc skimmer on their reef in the lobby. It is a recirc beckett Mr 3 they said

" it easyly out perform the MR-5 . it is because you can reduce the flow through the skimmer by half". FWIW

It mean nothing to me but FWIW thier recircs are doing great in sales.

 

[Roland Jacques]

<a href=showthread.php?s=&postid=8364278#post8364278 target=_blank>Originally posted</a> by pyrrhus
With a recirc skimmer you can indeed increase the bubble dwell time. All you need to do is restrict the air intake on the recirc pump. Less air flow=more water flow, which leads to greater entrainment of the bubbles in the water column leading to a longer bubble dwell time.

dont get what your saying at all? are your refering to the effects of the counter current.

 

[Zoom]

Ok what about my skimmer .
the skimmer is .
1) Swirl design.
2)Counter current
3) Recirc PW with two Eheim pumps
4) 40" tall by 10" diameter.

You think i can do better?

 

[alwest45]

Zoom/Steve, I've been on a quest for the "best" skimmer I can find for my new 240-300 gallon reef tank (mainly SPS with some fish and a few clams). Here's what I came up with:

1) Austin Oceans/Barr Aquatics Foaminator MAX 5000 (4' beckett skimmer, field upgradable to 2 becketts with a Sequence Tarpon pump (quiet and relatively low watts - for a beckett). This looks to me to be the best beckett skimmer out there and was my #1 pick. Does 45 scfh on a single beckett, 90 scfh if I upgrade to dual becketts (I like the easy doubling of airflow when my tank gets a little more crowded and needs a boost on performance). Very high quality construction and materials. Plus I couldn't find a single customer that had anything but praise for these skimmers. This was my #1 choice.

2) Euroreef RC250 with 2 Gen-X 4100 pumps with the new Euroreef impellor (supposed to do 76 scfh). A very solid and quality product plus only 30" tall so I could fit it under my stand if needed. Quiet and reliable. The rumor I hear is the ER is also improving their customer service so I've currently had this model as my number 1 pick. A little pricy but I'm looking for the best.

3) Deltec AP902 with 2 Eheim 1260 needlewheel pumps (56 scfh). A quality German skimmer and most of the people that have them love them - however, you will hear some grumbling if you listen closely. Quiet and reliable with top notch construction and materials. But you know that because this is what you have now!

4) H&S A200-2s1260 with 2 Eheim 1260 needlewheel pumps (56+? scfh). Another quality German skimmer that is similar to the Deltec but cheaper. Eheim pumps are very quiet and reliable. Not too tall either. I thought that ER customer service might be easier since they are in the US (I can hear those people that hate ER customer service groaning now). It won out over Deltec in my mind but could beat the ER or Austin Oceans skimmers on cost. Even though it is cheaper than Deltec it is a little dear too.

4) BubbleKing 250 External. A real bragging rights skimmer that performs well (53 scfh), is very quiet, and low on power usage. Top quality construction and materials too plus German cachet. And to top it off all your friends will be impressed you could talk you wife into spending this much for a skimmer - price tag was too much for me particularly since I could get better performing skimmers (AO & ER) for less. However, if you are looking for a conversation piece or a divorce.....



I think the Austin Oceans or Euroreef will deliver better performance than you are seeing with your Deltec. I really like the 2X performance kicker when you need it option on the Austin Oceans beckett skimmer (where else can you get another 45 scfh for $129 plus another pump?). But I'm currently sticking with the Euro-reef RC250 for it's out of the box simplicity and impressive 76 scfh performance.

That's my take on the "best performance" (not best value or lowest power usage or even most efficient power usage) skimmer today if you have a "starting to get large reef tank" (i.e. 200+ gallons). If you are under 100 gallons, then it's a whole new ballgame and I would probably still go with ER for their "short but a lot of air" (new impellor) designs. For 300 or larger (either now or a planned upgrade) I would definitely go with the Austin Oceans (Barr Aquatics) dual beckett skimmer.

Al

 

[sjm817]

AFAIK, the ER RC250 has a single SP5. The RC500 has 2xSP4, but the newest ones have 2 x Eheim 1262 pumps. Performance of the SP4 and Eheim are similar, but the Eheim is quieter.

 

[hahnmeister]

alwest45,
In my writing so far above, I termed dwell time as the time it takes for a bubble to rise from bottom to top, and contact time as the time the water spends inside the skimmer. So 'B', according to your question. The amount of time that the water spends in the skimmer matters somehow... the proof is in the puddin'... but there are theories.
1.Perhaps the dwell time can be interchanged with contact time (as in, they are the same)... the time it takes for one protein to get attracted to a bubble might be cumulative (the protein doesnt need to have 120seconds with one bubble but could be many)...in which case this is true. Otherwise, if they are not the same, it stilll suggests that the harder to capture proteins are still being drawn upwards in the skimmer, even if they are not extracted right away. In which case, they would eventually end up in the foam head where the remainder of the ideal 120second dwell time can be achieved. More throughput would mean there is a higher turnover, meaning less time with each protein.
2. Perhaps dwell time can not be interchanged 1:1 with contact time, but perhaps more contact can make up for dwell time... like a 4:1 ratio or something. So the lower throughput of a recirc skimmer would mean more contact time.
3. The lower throughput could raise the ORP more... causing better skimming. A higher throughput would mean the incoming fresh tank water would lower the ORP, and it would take that much more air to raise the ORP.
4. The countercurrent nature of recirc skimmers means fresh water enters at the top, and has to travel through the whole height of the skimmer before it exits the bottom. Single pass skimmers have the water and air enter near the bottom, just inches from the outlet. The water can travel 6" and exit, not like a recirc skimmer.

As for the theory, so far, the attraction of proteins that chemists describe doesnt take much of the physical account of how the two travel together. What, the bubble is moving, so does a protein just hang around the top waiting for the bubble to reach the right age before latching on and going out the top?

From what I remember, proteins naturally build up in the top layers of the aquarium water... the proteins and oils are less dense than saltwater. So all in all, it would be reasonable to suggest that a protein could be dragged up to the top, knocked off the bubble, but still remain in the top areas of the skimmer. The proteins have to travel with the bubble to some extent... dont they? I mean, the interaction of the air and bubbles has been suggested to be a mutually dependent variable, neither the air nor the water's time is independent... its the interaction between the two.

 

[alwest45]

<a href=showthread.php?s=&postid=8368223#post8368223 target=_blank>Originally posted</a> by sjm817
AFAIK, the ER RC250 has a single SP5. The RC500 has 2xSP4, but the newest ones have 2 x Eheim 1262 pumps. Performance of the SP4 and Eheim are similar, but the Eheim is quieter.

Arghh. Haste makes waste. Replace everytime I said RC250 with RC500. That's my current selection for my new tank setup, not the RC250. The performance numbers are for the RC500 with the new impellor.

The RC500 on the ER website still says 2xSP4. I would prefer Eheims though.

I originally was comparing the RC750 with the others on my list but when looking at the numbers it seemed that the RC500 would be a better match for comparison. Apparently when I was making my list today I stepped the ER down another notch....

 

[sherm71tank]

All this NW vs. Beckett talk inspired me. I switched out the 1/4" valve and air line I was using on my beckett with 3/8" and now I'm getting about 75 SCFH. So there! (Don't rain on my DIY parade to much guys!)

 

[alwest45]

Hahn, thanks for the more detailed explaination. I'm still struggling with the contact time, i.e. the time the water spends in the skimmer, and I have difficulty understanding the theory behind why this is good. Of your hypothesis #1 (dwell time and contact time may be 1:1 interchangeable), wouldn't this be true for all skimmers and not just recirc skimmers. In fact, wouldn't this be also true for beckett skimmers?

For #2, I understand the concept but don't see any reasonable theory as to why having the same partially skimmed water in the skimmer body makes for better skimming (other than perhaps the below)

For #3, you theorize that the ORP inside the skimmer body is driven up higher than the ORP in the reef tank itself and that higher ORP allows the proteins to more readily attach to bubbles or some other mechanism that makes for better skimming. I understand this point. Do you know of any evidence that supports this? This seems somewhat related to using ozone which will further reduce some organics and some people like to use ozone injected into the skimmer. As I understand it, Randy Holmes-Farley has weighed in on this topic and is of the opinion that ozone reduces the effectiveness of skimmers and that he recommends that if ozone is used it be used in small amounts. I understand that ozone uses a different process to raise ORP than skimming itself but given this data point with ozone do you think that the artificial raising of ORP inside the skimmer body actually improves the ability of targeted molecules to latch onto bubbles and be removed? (so far this is the only theory that I've seen that actually could explain why recirc water skims better so if this isn't true I'm back to square one).

FOr #4, what you say is certainly true. However, if we look beyond NW skimmers to becketts or DD skimmers, then you can see some longer bubble paths. And while some of those bubbles will certainly travel faster than a NW with a slow feed pump, some portion of the beckett bubbles will lose their momentum and travel at a normal bubble rise rate to the skimmer neck. One of the data points I noticed for the Austin Oceans/Barr skimmer was that the bubble path was over 100 inches. If this is important, then the Euro-reef RC500 that I'm planning for, which is only 30 inches in total height so the bubble travel distance is something closer to 24 inches, would be at a disadvantage. But this point I think does not explain the value of reskimming previously skimmed water - it just points out that if there is such a difference then recirc skimmers have an advantage. It's the theory behind the advantage I'm still searching for.

Btw, thanks for your time and efforts to convey your thinking on this - it has been very useful for me.

Al

 

[alwest45]

<a href=showthread.php?s=&postid=8368875#post8368875 target=_blank>Originally posted</a> by sherm71tank
All this NW vs. Beckett talk inspired me. I switched out the 1/4" valve and air line I was using on my beckett with 3/8" and now I'm getting about 75 SCFH. So there! (Don't rain on my DIY parade to much guys!)

Wow, talk about cheap horsepower. What was your scfh before?

Do you have a feel for how the skimmer performs vs. before at a lower scfh?

 

[sherm71tank]

It was about 50 before. Also, having owned DD skimmers before I can tell you that they have a significant impact on ORP where as the beckett, nw, venturi skimmers much less so. To soon to tell performance wise. I just got it done about 30 minutes ago.

 

[hahnmeister]

<a href=showthread.php?s=&postid=8369019#post8369019 target=_blank>Originally posted</a> by alwest45
Hahn, thanks for the more detailed explaination. I'm still struggling with the contact time, i.e. the time the water spends in the skimmer, and I have difficulty understanding the theory behind why this is good. Of your hypothesis #1 (dwell time and contact time may be 1:1 interchangeable), wouldn't this be true for all skimmers and not just recirc skimmers. In fact, wouldn't this be also true for beckett skimmers?

Im just going to address this because Im sure the rest dont want to have to read through it, and the questions you raise are many of the same ones I have. But with just the one above, yes, if they are interchangable, it would apply to all skimmers, which is exactly the point. Most single pass skimmers... venturi, beckett, needlewheel... they put water and air in at the bottom, and there is a very short path for the water to go before it can exit, which due to water's nature, it does take this path of least resistance. With a recirc, the path is from the top of the skimmer all the way to the bottom... much longer to begin with, and there is the greater contact time because while the single pass skimmer might circulate water through the skimmer at 400-600gph, the recirculating skimmer will only move 1/4 of that maybe... longer time in the skimmer = more crud pulled out. Logical, and one could say whats the advantage between skimming old and new... but if the overall exposure time is cumulative, then the older water that is recirculated would have the advantage. Maybe...

 

[Roland Jacques]

AL,
You picked some great skimmers choices, All of which will do a great job.

Shrem,
That sounds very cool. At 75 schf your skimmer needs a name now, how about the Sherm's Octobo-eckett skimmer. That's a lot of air you should post this.

Hahn,
I think AL wins, in his own example he disproves us. It’s kind of like this. You are the bubble and AL is the stubborn waste (strictly metaphorically ) . Other bubbles before you have bump into the waste with same info:spin1: :crazy1: :spin1: , but the waste keeps floating around, not bonding to it :bounce2: .

Most normal waste already let itself stick and is out of the way :beer: . So the other bubbles have moved on to be productive elsewhere :love2: . While you keep DWELLING with the stubborn waste, presenting the same info in many different ways and Examples and still, no sticking :bounce1: .

I guess the moral is like AL says, some waste going back into the system should be acceptable, so the bubbles can get on with trying to contact with new Poop.
Hmm I think he has got a good point .

(Pun intended):wave:

 

[NoSchwag]

Here's something my old needlewheel couldn't do...

You are looking at 1.5 days of SOLIDS collecting on my skimmer wall. It's all fish poop that you see. My tank stays particle free from my skimmer alone! Keep in mind my rocks are very clean

Another thing I couldn't do with my needlewheel is leave my house for more than a day without worrying if my collection cup would be full. The becket is VERY stable once running 100%. With my NW any little change in the tank would cause the skimmer to overflow, NOT TRUE WITH THE BECKET.

By matching my return pump to my skimmer pump, I skim my tank 9X's (give or take) pr. hour. This is something I couldn't do with a needlewheel or with a recirculating skimmer.

 

[sherm71tank]

<a href=showthread.php?s=&postid=8370682#post8370682 target=_blank>Originally posted</a> by Roland Jacques


Shrem,
That sounds very cool. At 75 schf your skimmer needs a name now, how about the Sherm's Octobo-eckett skimmer. That's a lot of air you should post this.

I'll try to get a pic tonight. I do lose a little on the air meter though as I have to reduce from the 3/8" to 1/4" due to the outlet of the air meter. On a side note I underestimated the foam head it was going to produce. This morning I woke up to a flooded waste container and a collection cup spewing wet foam. I lowered the water level and hope it doesn't flood while I'm at work! Damn thats a big foam head!