Skimmer capacity - What size skimmer is right?

[emora]

Hi everyone.

I see this question come up once and again... and again. Everyone wants to make sure their skimmer is properly dimensioned for their system but it seems that no one really knows what criteria to follow.

I think there is rather broad consensus that manufactuer specifications for skimmer capacity are rather "optimistic".

In the past I´ve taken the easy route and oversized. I chose a reputable manufacturer and chose a 300Gallon rated skimmer for my 100 Gallon tank. It seems to work well. How can I tell? I´m getting my daily cup of dense, dark skimmate.

But seriously, what criteria can we follow to dimension a skimmer to a tank?

We can look at water flow through the skimmer.

Now there´s talk more and more talk about air flow.

But what do these numbers mean? And what is the right ratio of water or air flow to tank volume?

 

[NaH2O]

Great topic! I'll be tagging along to learn....

 

[dnjan]

This question definitely has philosophical overtones.

First - are you married? In general, it is probably good to go with the largest skimmer you can afford, but sometimes wives can force a person to alter their perspective.

Second - what are you planning to keep? (what is their natural habitat?) For some corals, cleaner (more skimming) is better, while for others it is definitely possible to have too much of a good thing. (I traded a B. welsi frag to a friend with a pristine SPS tank a few years ago. He had it in a location with lighting similar to mine, but it got smaller and smaller until it finially died. In my underskimmed tank, however, both the parent colony and a frag I took at about the same time continue to flourish.)

Third - how much space do you have? Some of us need to fit our skimmers in the stand, along with the sump, pumps, etc. That can definitely be a limiting factor.

 

[emora]

Hey dnjan,

Yo are so ritght. There are many more criteria than just air flow or procesing rates. And what works for one system may be insuficient for another.

Nonetheless, there must be some comparable quantitative measures that we can use as guidelines. Size and price tend to be cut and dry. It either fits or it doesnt; you can afford it or you cant. The wife says shes ok with it... or you never know wether she approves or not (usually the latter... by default) XD

Aside from these cut and dry criteria what can we use to say, yep, this skimmer is enough or that one is too much. Is a 3000 Liter/hour air induction rate necessarily better than say 2500 L/hr? And for that matter, which measure is the most important?

 

[dnjan]

In addition to air volume per hour, you need to specify what is producing the air. Airstone (generally fairly fine bubbles, especially with wooden or the newer synthetic "stones"), venturi (slightly larger bubbles), beckett (generally larger bubbles), etc.

Looks like we are back to someplace between half of the manufacturer's lowest recommendation and what the wife will allow ...

 

[Skimmy]

currently formulating an intelligent response...it might take a while..lol

 

[Skimmy]

well you have touched on 2 of the important factors for choosing a skimmer, lph of air induction, gph of water processing...
but the criteria that actually make a skimmer a good one or not, also include a few other items...
1. reaction chamber diameter
2. reaction chamber volume
3. neck diameter and height
4. location of processed water output
5. size and diameter of skimmer output
6. method of controlling water level within skimmer
7. method of air induction
8. method of providing water to process
9. total watts consumed
10. materials used, and build quality
11. oh yes, and ease of use
12. and lastly, cost

so say you have a typical 4x2x2 120g reef, how do you figure out which skimmer is appropriate using the above criteria??
i'll answer that when i get back tonight

 

[dnjan]

One more factor I would add with respect to what makes a skimmer a good one or not is ease of cleaning/maintenance.

 

[DonW]

I think most of us have got caught up in all the super size, crazy design skimmer hype that we loose sight on the other things that make a reef successful. Ive had a 5ft 12" diameter monster, a moderately sized beckett and now a simple elcheapo asm g3 all on my tank. The water quality has not changed for the good or bad with the skimmer changes. The biggest changes came with stability. I think the name brand makers are pretty close in their estimation if we had FO systems. With sps systems I think its just common sense for the user to upsize a size or two.

Don

 

[Skimmy]

We can look at water flow through the skimmer.

Now there´s talk more and more talk about air flow.

But what do these numbers mean? And what is the right ratio of water or air flow to tank volume?

well, to use as an example, lets take euro reef skimmers,
in my opinion needle wheel and the new thread wheel skimmers are among the best to use because of their numbers, if you were to look at it like a formula it might be like:
watts consumed x
lph of air x
gph of processed water x
skimmer size & volume = "x" tank size
so look at this page at the euroreef site,
http://www.euro-reef.com/products-skimmerstechspec.shtml
it tells us all this info about each skimmer, further more it is pretty well accepted that they under rate their skimmers purposefully when comparing them to other companies(say deltec).
for instance,
lets take the euroreef rs180 vs. deltec ap600, both are rated from 130g -200g tanks, but they are totally different skimmers

the deltec ap600 recirc.(135g - 200g) specs are as follows:
lph of air =480
watts = 20w(aquabee 2000)
reaction chamber size = 5"
height = 22.5"
cost = $615

the euroreef rc180 recirc. specs are as follows:
lph of air = 960
watts = 45(gen x 4100)
reaction chamber size = 8"
height = 24"
cost = $825

so if you look at this, at face value it looks like the euroreef skimmer is way more expensive, but lets look at a deltec skimmer with the same numbers as the euroreef(notice how much more powerful the euro reef rated for the same size is)

deltec ap701 (rated for 250g-380g)
lph of air = 950
watts = 52 (eheim 1260)
reaction chamber size = 8"
height = 23"
cost = $1,080

so, deltec rates the same size skimmer for almost double the sized aquarium as the euro reef...
about the only real better thing on the deltec ap701 is the fact that it's a eheim pump, not a modded gen x pump like on the euroreef rc180, but the gen ex4100 out performes(until it breaks,lol) the eheim 1260, by just a hair, but we all know who makes the better pump there...lol

so, if we were to buy a euroreef skimmer with the same numbers as the deltec ap600(rated for 135-200g) for $615, it would be:

euroreef rc80
lph of air = 500
watts = 28 (sedra3500)
reaction chamber size = 5"
height = 22"
cost = $500!!
euroreef rates this skimmer for 50g - 80g!!! not 135g - 200g like deltec.

so you can see why i like to use euroreef as a benchmark to measure other skimmers and their ratings, i wish ALL companies would be so honest with thier ratings!!!

 

[Skimmy]

I think most of us have got caught up in all the super size, crazy design skimmer hype that we loose sight on the other things that make a reef successful.
Don

BLASPHEMY!!!!!!! lol

no, you are absolutely right, you cant be a one trick pony in this game, there are so many things that are also paramount to the success of a reef, the skimmer is just one thing...but an important thing, imo

 

[Skimmy]

i'll post more comparative information shortly....

 

[DonW]

Your not comparring apples to apples. There are differences in the two companies simmers other than tube size and how much air they pull in. Thats what makes the whole thing so difficult. Other than electrical efficiency watts has nothing to do with tank size rating.

Don

 

[Skimmy]

i realize watts have nothing to do with tank ratings, im just including it as comparable information for those who care how much watts they consume.
i was just trying to explain how some skimmers, even though they are rated for the same size system, came be vastly different, and giving people a FEW points on things to look for in good skimmer engineering from 2 of the leading skimmer manufacturers. there are no doubt other points that are just as paramount, and there are other skimmers i prefer over the ones i mentioned, but because the numbers on those skimmers were readily available, i used them.