Skimmer Volume Rating

[thriceanangel]

Does anyone know how they figure out that a skimmer is rated for a 300 gallon tank?? Is it just the volume or turnover of the skimmer? or just arbitrary? What if you add two skimmers? I would assume that because the second skimmer would be skimming some water that has already been skimmed, it would be less effective. So two skimmers that are each rated to skim up to 200 gallons, would not be capable of skimming 400 gallons if used on the same tank... Unless they were in tandem (?) Any insight is appreciated!

 

[Gary Majchrzak]

Skimmer volume rating is kind of like the kelvin rating on lighting- there is no "industry standard".
When it comes to skimmers, "oversize" and running wet is the way to go, IMO.

 

[Be1withthereef]

I'm not an expert skimmers or how manufacturers determine their numbers(profit driven) but I did find this page very useful. http://www.hawkfish.org/snailman/skimmer101.htm
The author states "you can go with more than one skimmer. However, if you do go with more than one skimmer, their total cross-sectional area needs to match pretty closely the cross-sectional area of the single skimmer diameter that is required for the project". He also has reference to diameter and flow charts for

 

[SteveL]

Agree with Gary - Skimmer recommeded size is NOTHING more than a recommendation. As a buyer you have to accept this - it's not the fault of the vendors because it's like asking "how long is a piece of string".

For example - you can run a successful system without any skimmer - just ask Julian Sprung about his tanks where he travels a lot and has to keep tanks at home very simple (i.e. no skimmer). At the other extreme you can skim the living daylights out of a system allowing you to keep more fish and feed more nutrients into the system. It all depends on what you are trying to do and the equilibrium (balance) you have trying to maintain.

I can't over emphasize the philosophy that it's a balance that you are trying to establish then maintain and skimming is just one of the tools we have at our disposal to achieve this. Otherwise size of skimmer is only a recommendation based off current practices and expectations we have established in the hobby of a what constitutes a reef tank.

In summary my recomendation is also to go bigger on skimmer rather than smaller - it gives a safety buffer for growing fish, increased food input and overlooked maintenance.

SteveL

 

[thriceanangel]

But it has to based somewhere in reality doesn't it? Because if I were a vendor, and less than on the up and up, I could rate my skimmer for say 400 gallons, when in reality it won't skim anywhere near that amount. I mean at least in the eyes of a vendor, there has to be some foundation I would think. If one vendor is basing it on bubble counts, while the next is using flow volume... at least thats something. It's not consistant, but at least its not completely arbitrary.

When I buy a piece of string, I ask for or buy the length thats on the container. If it says 4 ft of string, but I open it up and there is only 2 ft, there is going to be a problem. Even if it says use only where 2 ft of string is appropriate.

BUT if thats true that it is based more on the locations of the stars than on some concrete evidence, than there has to be some vendors that are pretty close to reality. I know that ASM and a few others recommend lower than what you could use.

But the second part of the question remains, what if you are using 2 skimmers?? (edit) Sorry I missed the part on the 2 skimmers.

 

[SkiFletch]

Well, I think the point is that skimmers are rated on subjective oppinion as opposed to objective data. I'm sure that manufacturers do their best to rate skimmers appropriately however its nearly impossible to rate a skimmer using objective data since their operation is so variable.

As for running two skimmers at once, if they are both ran in-sump I'd imagine you'd get good performance out of each (provided they are similar size). However if you run two inline skimmers which I'm not sure is even probable from an engineering standpoint, you'll get drastically reduced performance of the second

 

[Kent E]

In my opinion, there should be a new standard of the skimmers volume itself. When you know the skimmers volume you can use your own scale to determine whether a skimmer is large enough.

 

[SkiFletch]

Agreed Kent, but at the risk of playing devlis' advocate, might the ability of the pump to create microbubbles be equally as important as skimmer size, if not more important?

 

[Kent E]

Sure. But how do you measure that?

That's the problem with skimmer size recommendations.

On the positive side, I think skimmers are closer in performance than they used to be, discluding the really junky ones.

 

[SkiFletch]

In theory you could rate skimmers by weight of dried skimmate produced per unit time, but its REALLY hard to accurately do those measurements and maintain good controls and data collection practices, hence they've never been done.

I definitely agree that skimmers are having much better performance when you exclude the cheapies

 

[thriceanangel]

So when a manufacturer of a "cheapie" skimmer claims that it will skim 300 gal, are they lieing? Would said skimmer be useful on a 90 gal tank? I just look at all the skimmers out there, and I wonder where the truth lies. I wouldn't want to spend $300 for something that I can get for $179. I know that the $300 skimmer would be overkill, but what about the $179 skimmer. Is it totally junk? I have seen them produce plenty of skimmate, but are they as effective as the $300 overkill? Probably not.

There should be a way to test these things. What about if you had a protein based dye. And put a known amount of dye in x amount of salt water. Then tested the amount of time it takes to remove the dye, or an accepted amount of the dye?? It'd be slightly less than scientifically perfect, but I think that it would be a reasonable test.

 

[thriceanangel]

Does anyone think that this will work?

 

[SkiFletch]

In theory it would, but you'd have to find just the right dye. I remember when my sea hare inked and the skimmer cleared that dye up so fast that I didnt even know it had inked until I finally figured out that was what the red stuff in my skimmer was... You'd need to get a protein dye that was slow enough in skimming to offer some parody between skimmers.