Skimmer Ratings- a discussion.

[Powerman]

Sort of thinking out loud here. Just wanted some thoughts on how skimmers are rated and what goes into that.

There are some rules of thumb in our hobby, but no such rules for skimmers. Air draw/gallon, water flow/gallon. What turn over rate? How about air/water ratio? We have been using skimmers for quite some time now, yet there is no established guide lines for how much air, water or turnover you need for a system.

Take the well documented Sicce PSK 2500. Mate it to a ton of different bodies and get ratings of anywhere between 90g-200g. While the performance can be changed with different wheels, venturies, and bodies... the pump will still do a certain air/water flow range and flow ratio. Yet there can still be some big claims and wide variation of what it can handle.

Here is another example. I feel the 600 lph I was getting on my BK Mini 160 was good for my 90g. I feel the 1000 lph I'm getting from my K2 is overkill. Seems a popular range and air draw these days. I asked a while back for air draw on Beckett skimmers. What I ended up with was a gentleman that was getting 35-50 scfh on a single Beckett. His seemed to operate best at 37 scfh. That is the same I'm getting on my K2 on my 90g, yet this Beckett was on a 500g system and the owner felt is was the best skimmer he's ever had. So how can 37scfh be good on 90-180g systems, yet be claimed to be plenty of air for a 500g system?

There is plenty I would like to discuss, but don't want to make the opening post too long. I think you get my point.

 

[Powerman]

Oh, here is a second point I would like to discuss.... a skimmer rated for 120g heavily stocked. Bio load and stocking levels could not be any more arbitrary. I mean, does anyone really know how to measure a "bio load"? I can tell you I have two Tangs in my 90g, but so what? They are small tangs.

Also we all know a skimmer will only skim what is there. So a 120g rating on heavy bio load..... does that mean the skimmer is operating 100% of the time....no extra room...all out.... still has 10% reserve. Comfortably handle a 120g, or the limit and any upset will be "over the limit".

See what I mean?

 

[VanGogh121]

I was talking to a fellow reefer ( And highly respected) about 7 months ago about this, He figured the best calculation is LPH of air pushed though the skimmer. It has been a long time but if I remember correctly he calculated it to 500 LPH for every 100 gallons. It seemed pretty accurate, as real world calculations seemed to match his calculations.

 

[mojo]

Well its not just air flow. its water volume, flow contact time and how efficient it works as well.

 

[Powerman]

I agree with the 500 lph for a general rul. Let's just say the skimmers will be properly built to give adequate contact time...... As Mojo pointed out, air draw isn't everything. 500 lph with a water flow rate of 100 gph would probably not accomplish much. Plus, skimmers have been doing well for some time and they were not always pulling the air numbers todays needle wheels are pulling.

Air draw is very easy to measure, but it is much harder fro water, not to mention it isn't going to be a set number just like air. It depends on water level. Even still, I would like to see more water processing rates by manufacturures and what is an appropriate tank turn over rate.

Just look at recircs.... tank turn over rate would be very different.

 

[Troylee]

My big cone skimmer I built for my 500 pulled 47scfms and it was a big boy 16base 24 tall with. 6.5" neck that was the cone body size the whole slimmer stood 38" tall and it ran like a champ if I added more mesh the airdraw would increase but so did wattage, turbulence etc.. It started to go out of balance and actually ran best around 40 to 45 cfms... My new skimmer the atb replica runs at 37 and I have not even tryed to change it and see if it gets better or worse I just fired it up and it ran so well I just moved on to the next step my stand when I get some time I might play with it... There is a ton of varibles in even trying to rate a skimmer that's why for the most part people buy twice the size they need... In reality I don't think you really can put any exact numbers on a skimmer for wattage draw, airdraw, or a tank rating.... I can tell you this much mt tank is 220gal running volume and my skimmer will pull good for like 20 min every 3 or 4 hours and almost idols the rest of the time.. Atb rates it for 579 gal and I'm sure it could prolly hang with it since I got a heavy load like 17 fish now and 6 of them are large tangs and this thing still don't produce all day everyday...

 

[Powerman]

And that is a good point. I had a Mini BK that I thought was a bit small. Maybe I got taken in by air draw. Bubble King rates it to 135g. Well I got a K2.... I won't say it was a waste, and I want to move up to a 180g.... yet now I know the Mini 160 was doing fine. My K2 produces probably half the time. I would say a bit more than the Mini 160, but it idles a lot more.

So then some folks say go twice your system volume. So if you had a skimmer rated for 90g, then it should produce 100% of the time. So one twice as big should idle 50% of the time. Now assuming you have no plans to go bigger, what would the point be to buy a skimmer that runs 100% of the time, yet only produces fro 50% of the time?

At least the time a skimmer produces fro starts to give an idea of how well it is working... that is assuming that the time it is not producing means there is no organics it can skim.

 

[Powerman]

My big cone skimmer I built for my 500 pulled 47scfms and it was a big boy 16base 24 tall with. 6.5" neck that was the cone body size the whole slimmer stood 38" tall and it ran like a champ if I added more mesh the airdraw would increase but so did wattage, turbulence etc.. It started to go out of balance and actually ran best around 40 to 45 cfms... My new skimmer the atb replica runs at 37 and I have not even tryed to change it and see if it gets better or worse I just fired it up and it ran so well I just moved on to the next step my stand when I get some time I might play with it... There is a ton of varibles in even trying to rate a skimmer that's why for the most part people buy twice the size they need... In reality I don't think you really can put any exact numbers on a skimmer for wattage draw, airdraw, or a tank rating.... I can tell you this much mt tank is 220gal running volume and my skimmer will pull good for like 20 min every 3 or 4 hours and almost idols the rest of the time.. Atb rates it for 579 gal and I'm sure it could prolly hang with it since I got a heavy load like 17 fish now and 6 of them are large tangs and this thing still don't produce all day everyday...

So then tell me Troy... with all the skimmers you have built, and some you have copied... how do you personally go about telling what a skimmer can and can't handle?

I mean besides taking others manufacturers word for it and copying their dimensions... how do you take a skimmer and size it for a tank?

 

[Troylee]

Air draw, contact time and estimating off the current ratings manufacturers suggest on there skimmers... How they come up with the numbers is kinda far fetched like I said you can't really give any exact specs just a guesstimate really there is to many variables involved...Pretty much I think you would have to place the skimmer in question in the same secanrio but on different volume tanks and see where it performs to even get a close guess... Personally I look at the manufactures who stay on top and keep changing there skimmers to stay on top like atb or octos they keep coming out with new lines to keep up with the times if ya don't you will be gone tomorrow IMO. I think alot of manufactures use it as selling points, some in a good way and some are so fetched it's just plain stupid like seaclone the 150 is good for a aquapod and that's about it, why are they still around?!? We all know they don't work but all the newbs keep buying them so stores keep putting them on them shelves....Swc Is another one that's constantly changing designs and working towards the future with new designs every few months... It's really hard to build a skimmer that will fit everyone needs because everyones system is different and the skimmer performs different everywhere it is put.... A classic example is set up a skimmer in a rubber maid with some saltwater and run it after a few hours add the skimate from your tank that took 3 days to get that skimmer will pull it in like 10 minutes and you will notice increased air draw at the moment you add the skimate the thing will go from milky white to solid white in seconds.... This is just speaking from exp. I'm not a scientist or anything just like to play and test and play...

 

[Powerman]

Thanks Troy.... I think like you said you would have to put a skimmer on established tanks of different sizes and just find out where it can't keep up anymore...... but even then we are back to how you measure bioload. A Company could have an established tank, but fish still grow. I would find it very difficult to have a 180 that will never change the biolaod on it. Perhaps it is close enough to call good.

In your experience Troy.... when you see a tank rating... do you see that as maxed out... with a 10% reserve fudge factor... or what you should have on a tank?

I mean personally.... If I got a skimmer RATED for my tank, I would want one that would have 25% head room just to know I'm on top, or be able to handle a dead fish back in a rock. So do you think most ratings are a "max" or is there some reserve figured in?

 

[Powerman]

I also know there is a lot more experience on this board and a lot of vendors too. I would love to hear from some of you guys too.

 

[Troylee]

i cant really answer that since i have only played with all my skimmers on 4 different size tanks and i have not tried every skimmer out there to really compare there claims to tanks to see....mojo would be the one with all the exp. on different skimmers but im sure they all ran on the same size tank or 2 maybe, since us hobbiest don't have a million tanks and a million different size skimmers to actually see....that would need a actuall company to step in and answer correctly or at least give there sense on how they do it..

where is all this coming from and what are you trying to get at if you don't mind me asking???

 

[Jeremy R.]

I rate our skimmers more on hands on experience of certain models. Things to look at are the overall design, the pumps output, flow through rate (water processed), contact time/turbulence and a very important and often looked over factor is the neck size. The idea of oversizing a skimmer with most skimmer models we carry will actually do more harm than good. I am a firm believer in picking the correct skimmer for the size of the Display/load.

 

[Powerman]

I rate our skimmers more on hands on experience of certain models. Things to look at are the overall design, the pumps output, flow through rate (water processed), contact time/turbulence and a very important and often looked over factor is the neck size. The idea of oversizing a skimmer with most skimmer models we carry will actually do more harm than good. I am a firm believer in picking the correct skimmer for the size of the Display/load.

Thanks a bunch Jeremy..... So then... when you look at those things, how do you determine water flow rates?

Also, I understand larger necks with smaller bio loads.... so when you say the correct size skimmer for the tank... what does that mean? 100% capacity, 110%, 125%.. do you think those extra factors are built in? Would you put a skimmer rated for 90g on a 90g tank?

 

[Powerman]

where is all this coming from and what are you trying to get at if you don't mind me asking???

I like the hobby, but I have always been a sucker for gear. I like skimmers. Some of you guys are a trip.... I think you have reef tanks just to run skimmers

Anyway, I just like learning. This question comes up a million times. I am trying to write an article on another forum. It isn't really for a specific reason, just curiosity and trying to tackle the question head on instead of "is this skimmer good for this tank?"

 

[mojo]

I rate our skimmers more on hands on experience of certain models. Things to look at are the overall design, the pumps output, flow through rate (water processed), contact time/turbulence and a very important and often looked over factor is the neck size. The idea of oversizing a skimmer with most skimmer models we carry will actually do more harm than good. I am a firm believer in picking the correct skimmer for the size of the Display/load.

I totally agree.

 

[Troylee]

Okay but how and were are you getting this rating?? Besides guesstimating... Just taking the manufactures word for it?

 

[Jeremy R.]

Okay but how and were are you getting this rating?? Besides guesstimating... Just taking the manufactures word for it?

Not guesstimating, experience. I test them out first hand. I get many prototypes prior to production for testing from various companies and offer design innovations. I have used, tested and or had hands on experience with over 30 different skimmers over the past 7 years or so including venturi, beckett, downdraft, pinwheel, meshwheel, needle wheel, spray injection, etc. My ratings are my personal suggestions of what I would place on a given tank and do not inflate the numbers what so ever. My goal is to get the customer the very best performing product for their given system. There are always exceptions to the rules and the ratings are only to give the customer a ballpark range.

 

[Troylee]

I got cha and feel the same way... I have done tons of testing and like you say it's a ball park figure... I dont think anyone can give a exact estimate but they can come close which in my eyes is good enough that's why I error on the side of caution and always think long term..... I think the best way about going to buy a skimmer is look at what you can afford and get the job done for that amount of money and buy the next size up spend the little extra dough and you will never be dissapointed IMO...

 

[Powerman]

Not guesstimating, experience. I test them out first hand. I get many prototypes prior to production for testing from various companies and offer design innovations. I have used, tested and or had hands on experience with over 30 different skimmers over the past 7 years or so including venturi, beckett, downdraft, pinwheel, meshwheel, needle wheel, spray injection, etc. My ratings are my personal suggestions of what I would place on a given tank and do not inflate the numbers what so ever. My goal is to get the customer the very best performing product for their given system. There are always exceptions to the rules and the ratings are only to give the customer a ballpark range.

So then, understanding it is not a difinitve number and just a ball park..... what ever number you come up with..... how do you rate?

Say you say a skimmer is rated AT 90g tank. Is that at full capacity, with 10% head room, 20%? Not trying to ask you to pin point, I asking what factor do you feel is a good fit for a given tank? 1 times, 1.1, 1.25, 1.5 times?