Over Skimming - Is it Real

Ljaus · Dec 12, 2016

From my understanding the overskimming theory came from reefers running downdraft and Beckett skimmers which have a longer contact time which supposedly led to the risk of overskimming.

Well that's what I've read anyway.

I've always had a bigger skimmer than needed. Never had a problem.

redfishbluefish · Dec 12, 2016

Ljaus said:
From my understanding the overskimming theory came from reefers running downdraft and Beckett skimmers ...........

Interesting. The MRC skimmers I ran were not downdraft, but they were beckett skimmers. Noisy as all heck, and required big pumps, but very efficient.

Ljaus · Dec 12, 2016

redfishbluefish said:
Interesting. The MRC skimmers I ran were not downdraft, but they were beckett skimmers. Noisy as all heck, and required big pumps, but very efficient.

Like I said just from what I read once. Don't know how true it is. Trying to find where I read it

ritter6788 · Dec 12, 2016

I ran a Reef octopus rated for 200 gallons on my 75 gal. and a vertex rated for 150 on my 40 breeder. I always ran the biggest skimmer I could fit in my sump/stand.

Orcus Varuna · Dec 13, 2016

I never understood the theory of why people think over-skimming exists. If their are not enough organics in the water column to support a sufficient foam, the skimmer can not remove anything else. They should in theory be self limiting. Now is a skimmer too large for your tank is another question completely. If I put a giant skimmer on a small tank the amount of organics may not be enough to support a proper foam, thus it won't remove anything. But even in this scenario you would not be over-skimming but under-skimming... Please correct me if I am wrong.

Randy Holmes-Farley · Dec 13, 2016

Orcus Varuna said:
I never understood the theory of why people think over-skimming exists. If their are not enough organics in the water column to support a sufficient foam, the skimmer can not remove anything else. They should in theory be self limiting. Now is a skimmer too large for your tank is another question completely. If I put a giant skimmer on a small tank the amount of organics may not be enough to support a proper foam, thus it won't remove anything. But even in this scenario you would not be over-skimming but under-skimming... Please correct me if I am wrong.

Self limiting at no soluble or particulate organics or bacteria in the water would likely be quite undesirable as no filter feeders would survive without target feeding.

The issue is that such a thing does not seem attainable with available skimming technology.

Orcus Varuna · Dec 13, 2016

Randy Holmes-Farley said:
Self limiting at no soluble or particulate organics or bacteria in the water would likely be quite undesirable as no filter feeders would survive without target feeding.

The issue is that such a thing does not seem attainable with available skimming technology.

Thank you for the clarification!

klp · Dec 16, 2016

Randy Holmes-Farley said:
Self limiting at no soluble or particulate organics or bacteria in the water would likely be quite undesirable as no filter feeders would survive without target feeding.

The issue is that such a thing does not seem attainable with available skimming technology.

That was my thoughts exactly on both statements. Is it possible for say a 200 gallon rated skimmer on a 40 gallon tank to take everything out or are we still at the approximate 30% level of removal due to current skimmer technology? Would it just work faster in that case or would it strip the water? I always thought the 30% figure was because the skimmer does not skim all the water constantly just a portion of it. That would mean bigger portion more removal. Inquiring minds want to know..

Randy Holmes-Farley · Dec 16, 2016

IMO, it is an open question of what actually remains in the water after heavy skimming. TOC doesn't say what the residual materials are, or even whether they have any substantial biological availability. Identifying particulate organics is quite difficult, and even soluble organics require extensive research to pin down exactly what they are.

luke33 · Dec 16, 2016

This thread comes up every year and I see the same thing every time. Someone says that there was an advanced article and skimmers can only pull 30% of blah blah, others say you can't overskim and then there are other theories about it. Its always a fun article. I'll give my same thoughts I have been giving for the last 7yrs or so.

Advanced Article - To say every skimmer out there can only pull out 30% organics seems really odd imo. I don't believe this to be true personally. It would be fun to see another updated article with more advanced skimmers since so much has changed in the hobby in the past 10yrs. The article was also done in the middle of the skimmer wars back in the day, which was an interesting and argumentative time. In order to have a nice skimmer you had to really spend the coin or modify it vs just buying it and dropping it in your tank these days.
You can't overskim! - IMO this can happen but rarely does. In the only time i've seen a tank become sterile it was due to carbon dosing, medium feedings and having a well fit skimmer for the system
To big of skimmer - If you have to large of skimmer, mostly neck diameter, your skimmer will skim inconsistent. Meaning it will have a foam head for a while and then fizz like soda for a while. The problem with large neck diameter skimmers is it takes a whole lot of organics to fill the neck, then to push it to the collection cup takes even more organics.

Brew12 · Dec 16, 2016

If your goal is an ultra low nutrient system I'm not sure how you could over skim.
If your goal is a zoa garden then I see how you could over skim.

What are we using as the definition of over skimming?

Randy Holmes-Farley · Dec 16, 2016

Brew12 said:
If your goal is an ultra low nutrient system I'm not sure how you could over skim.
If your goal is a zoa garden then I see how you could over skim.

What are we using as the definition of over skimming?

Presumably it means skimming so that the tank would do "better" with less.

Lots of people are beginning to have nutrients too low, even for SPS, so it doesn't seem far fetched to me that skimming heavy contributes to this issue.

Brew12 · Dec 16, 2016

Randy Holmes-Farley said:
Presumably it means skimming so that the tank would do "better" with less.

Lots of people are beginning to have nutrients too low, even for SPS, so it doesn't seem far fetched to me that skimming heavy contributes to this issue.

Have you seen people who say their nutrients are too low that don't use GFO and/or carbon dose? Or use algae scrubbers?

redfishbluefish · Dec 16, 2016

Randy Holmes-Farley said:
Presumably it means skimming so that the tank would do "better" with less.

Lots of people are beginning to have nutrients too low, even for SPS, so it doesn't seem far fetched to me that skimming heavy contributes to this issue.

But this is always in combination with carbon dosing (or some other means to remove too much N and P.) So not the "fault" of the skimmer.

4FordFamily · Dec 16, 2016

I too highly doubt you can overskim, although I don't keep anything other than beginner coral... but I imagine most advanced coral would prefer cleaner water so I just can't imagine a scenario where you can truly overskim. The largely unsung fact about skimmers these days is how well they oxygenate the water. If you want to keep tangs they love it.

Paul B · Dec 16, 2016

Randy Holmes-Farley said:
Identifying particulate organics is quite difficult, and even soluble organics require extensive research to pin down exactly what they are.

I believe any particulate matter can be removed by a skimmer just because of the surface tension of the bubbles. I see new born brine shrimp in my skimmer as well as any left over food and detritus. When I use my diatom filter I find diatom powder in the skimmer and that stuff is inert.

Randy Holmes-Farley · Dec 16, 2016

Brew12 said:
Have you seen people who say their nutrients are too low that don't use GFO and/or carbon dose? Or use algae scrubbers?

yes.

Just 2 days ago:

https://www.reef2reef.com/threads/how-can-i-get-some-nutrients-in-my-tank.278757/

Randy Holmes-Farley · Dec 16, 2016

redfishbluefish said:
But this is always in combination with carbon dosing (or some other means to remove too much N and P.) So not the "fault" of the skimmer.

Not always.

saltyfilmfolks · Dec 16, 2016

Brew12 said:
Have you seen people who say their nutrients are too low that don't use GFO and/or carbon dose? Or use algae scrubbers?

At My house. In the 55 (refugium), The 30, skimmerless most of this year

and Fuge less too.

And five times a week on R2R.
because of this.

Paul B said:
I believe any particulate matter can be removed by a skimmer just because of the surface tension of the bubbles. .

IMO its why feed hard skim hard works.
But also worthy of note I belive, I have to feed my tanks more than the fish will eat. Or my nutrints drop.

Joseph Pagnotta · Dec 16, 2016

I'm running an Eshopps Psk 150 in My 55 gallon reef. Not an issue with my tank.
I have 7 Fish and Many Corals with About 120 lbs live rock and Black tahitian moon sand for my substrate