Skimmer sizing?

ultimatemj

ultimatemj

Active member
I'm wondering if anyone has seen mathematical approaches to skimmer sizing...

You regularly hear "it is good to oversize a skimmer", but oversizing too much can easily lead to poor performance, as there is not enough organics in the water for the skimmer to work properly (will either work very inconsistently, or the skimmate will not be able to make it up and over the collection cup).

There don't seem to be any standards for "rated for tanks from x to y" and there is this vague "loading" thing thrown around...Heavy, moderate, or light "loading"....with no reference for what that really means. :rant:

Does something like "inches of fish per gallon" play into it? Gotta think Tangs should count for double their length! LOL

What about corals? Do the different types(LPS, SPS, softies, inverts) make a difference?

Quantity, or type, of food put in tank each day? 1 cube, 2 cube or pinch o' pellets, or? LOL

Then there is the whole "probiotics" topic (biopellets, voka, vinegar, sugar, VitC, etc) that often states "you need to increase skimming"​

I've got to think flow rate relative to total water volume is a starting point, but then there are recirculating skimmers that probably makes that math more complicated

Without going through all the skimmer factors, it would seem chamber diameter (4", 5", etc) is the primary factor...but there are no tangible references for when to upsize or downsize.

Here's my situation: 55g display tank, a ~22g sump, and 25' of plumbing (~7g) between them (sump in basement). Live rock is probably 15g worth of space and the sump probably has 4g of equipment and media space used. Approximately ~65g total water volume.

Current skimmer: Coralife 65 generates enough coffee skimmate that it needs emptied weekly, but it seems there are more nutrients in the water than it's pulling.

Flow-wise, I've got way more return pump than I needed. I was worried about the 25' of plumbing head pressure, and possibly adding a chiller to run through. I had to close the ball valve half way to throttle back the HY-10000 to something like 700gph. Good news is it's not even drawing 3amps!

Fish-wise, I've got a Johnsoni wrasse, a Coral Beauty, a yellow assessor, a clown goby and a pair of cardinals. And I expect to add another wrasse.

Coral-wise, I've got a full mixed reef (softies, LPS, SPS, NPS, etc).​


All the 4" chamber skimmers I'm finding have "lesser pumps" spec'd on them. And upgrading a pump on a 4" makes it cost more than a 5" or 6" with a good pump :(

I like the AquaMaxx CO-1, but I'm concerned it's 5" chamber could be "too big" for my tank and I'd simply be wasting time and money on a "nicer skimmer". It is rated for aquariums 175-500 gallons!

:hmmmm2:

Thoughts?
 
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There's plenty to look at, but the biggest thing I want to mention from your post is the neck size being too long to allow for the skimate to make it to the top.

If you adjust and tune the skimmer correctly, and assuming it has conditions such as correct water height, you should not experience that problem, regardless if it is oversized or not. I've thrown a "rated 300g skimmer" on a 40g cube.

The rest comes into acct from waste, and how often and heavy you feed, the more you feed the more that will turn into waste that can be skimmer. There's no end to opinions on flow rates of water through the sump that effect the skimmer. I also think depending on the type of skimmer you have, that you might want to adjust accordingly. I think most people forget that different things require different environments to work to the best of their ability and therefore people have items that underperform due to this. I prefer to pump water up slower and make more current through power heads for two main reasons. One, to provide more time for my skimmer to skimmer whats down there, and two, less like to have turbulent conditions in the sump and pipes. I also always wanted less water speed running through my fuge area for the macro and pods to have nice calm conditions.

In short, I'd recommend not worrying much about the neck height as long as you can provide ideal water height that is stable for the skimmer, the rest can be tuned to make sure your concern of the skim mate making it to the top is taken care of.
 
Thanks for the response Gary,

Maintaining water height is not a concern, as the ATO maintains a constant water depth in the sump and therefore a "constant tune" on my skimmer.

My chamber size concern is about the diameter and its impact on the "concentration of head". Meaning, a given amount of solids have to precipitate out and "climb into the cup". And an 8" diameter chamber with the same "waste" is 4times "less concentrated" than a 4" diameter.

Granted 4" to 5" is "only" a 1.5 multiplier...

Maybe I'll just try it and find out :biggrin1:
 
This is really a great question, I have a eshopps 200g snow cone skimmer in a 29g sump on a 40breeder DT and have concerns that it'll be too much. Definitely gonna tag along.
 
I don't turn my skimmer off during feeds, so I never worry about the waste waiting to be moved up getting put back into the system, I prefer to run my skimmer very dry, so I instead deal with the nasty cone cleaning, but my nasty get stuck around there.
 
Just to chime in on the protein skimmer question/ statement, I believe it is always good to use an oversize skimmer opposed to a smaller one. I find it is good to have one that has adjustable skim rates to control the generation of micro bubbles needed to skim. As mentioned in your post, an oversized skimmer tends to do lots of wet skimming because of the absences of organically in the water column. Yes, lots of water will be used, but, wet skimming is a perpetual water changes that helps the water parameters. To achieve thicker skim mate, adjust the air flow by significantly cutting the air supply causing a thicker and more concentrated form in the skim cup.


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