What does "over skimming" actually mean?

[MikeBrke]

I ask because it seems this is the directions alot of people are going with their tanks. For example, people using skimmers rated for 150 gallon tanks on their 90 gallon (sps dominated, light/medium stocked) tanks?

So:
1) what is "over skimming" and how is it bad?

2) Is it theoretically better to over skim? Is their a real benefit or is it the "bigger is better" mentality?

Thanks,

Mike

 

[kysard1]

If a skimmer is too big there isn't enough DOC's to hold a head of foam. It literally won't skim.

 

[DrBDC]

By the same token, the manufacturers severely overrate thier skimmers. Usually they state double the size they are adequate for.

 

[MCsaxmaster]

I'd define overskimming as skimming a tank so aggressively (having such a large skimmer) as to limit the food intake of desirable suspension feeders, or even cause outright starvation. Typically this happens when people put monsterously large skimmers (for a given tank size) on their tank and provide very limited amounts of food to the tank. Skimmes are so large and efficient nowadays that many skimmers can, if misused, outcompete many suspension feeders (including sabellid/serpulid worms, sponges, bivalves, corals, etc.) for particulate food to the detriment of those animals.

I think it is advantageous to have a large skimmer that can pull out a lot of organic material if needed, but to limit the use of that skimmer to what is really necessary to keep the system healthy. The goal is not to strip all the particulates out of the water because so doing will starve your suspension feeders. Often this lends to a very "sterile" looking tank that, IME, is much more prone to problems.

cj

 

[madadi]

i have a PM bullet-3 on my 90 gallon and its run with an iwaki 70r pump so its skimming like crazy. the skimmer is rated for 400gallons. its probably the best thing to ever happen to my fish tank. i do feed a lot. 2, 3 times a day. i like fat fish and the large skimmer allows me to do that without worry. i have to clean the collection cup every 3 days. i think bigger is better, unless your sump empties when your skimmer is turned on, then your pushing it and you need to take it easy on the skimming and spend your money on other equipment as well.

 

[hahnmeister]

A PM bullet 3 on a 90g isnt too crazy really. An Iwaki 70 is a bit of a power hog, and provides some great pressure, so its most likely getting a good 1600-2000lph of air. Not exactly overkill if you feed your fish like a 180g.

 

[Wrassemeister]

so would you guys consider a tunze 9015 to be overkill on my 35gal or does it depend on my bio load?

 

[hahnmeister]

Considering it can handle a tank 10x yours... yeah... thats overskimming.

 

[ta_lewis]

Well guys am i over skimming I use a ASM G4x+ on my 90 gal. It fills the cup about half way full every 3 days and I feed everyday.

 

[Julio]

i don't believe the term over skimming can actually be done in captivity although many people say so, if you the water quality in captivity won't ever match that of natural sea water although in some case it come sclose, but never equal.

 

[MCsaxmaster]

I've seen it done many, many times, so I assure you, it can be done

 

[Wrassemeister]

well there is always the option of putting the skimmer on a timer for 12 hours a day or so...

 

[DrBDC]

Back in the early 90's, it was a common myth that was espoused by those opposed to the "new" ways. Those 1 ft airstone skimmers were the blame for everything wrong. Well except for what all the bristle worms killed.

 

[kysard1]

A too big skimmer actually won't skim as much as a properly sized unit.

 

[Lutefisk]

<a href=showthread.php?s=&postid=11058489#post11058489 target=_blank>Originally posted</a> by Julio
i don't believe the term over skimming can actually be done in captivity although many people say so, if you the water quality in captivity won't ever match that of natural sea water although in some case it come sclose, but never equal.

The virgin reef has very clean water. It also has far MORE food for coral and fish than our reefs.

 

[demonsp]

<a href=showthread.php?s=&postid=11058917#post11058917 target=_blank>Originally posted</a> by Wrassemeister
well there is always the option of putting the skimmer on a timer for 12 hours a day or so...

I agree with this. If the skimmer is crazy big then dont use full time and also turn off while feeding. It is better to get a larger rated skimmer then you need but i dont think you can over skim.

 

[jerryz]

Wouldn't an "overskimmed" tank just not have any proteins attach to the foam? Also not sure how this would be intrinsically bad. Can anyone cite a study showing that corals feed on the type of proteins that are attached to bubbles during fractionation? That would seem improbable but I'm open to proof.

 

[MCsaxmaster]

It is fairly easy and reasonably common to have NSW levels of dissolved inorganic N and P. In captivity DON and DOP are often somewhat elevated compared to nature, but a bigger skimmer may not change this. There is also much, much less plankton and POM in most tanks as compared to nature. Skimmers can exacerbate this problem.

cj

 

[jerryz]

Nice statement. Back to the citations please. Sorry come from a scientific background

 

[Fishbulb2]

There's no real research for this kind of stuff. It's a hobby. There's no peer reviewed journals or government funding for these questions. Comparing reef tanks to natural reefs is rather low on NSF and NIH funding. Good thing too. The experience of board members is all we can use.
Sorry,
FB