Wet Foam vs. Dry Foam

[tankgirl2]

I know some of the mods here recommend wet foam production from a skimmer.

But, when I do a search (wet/dry foam) every single result I found recommends dry foam production - almost all based on the following reasoning;

If the foam contains a lot of protein, however, the upper bubbles reform into a "dry" foam that contains less water and more organics. This dry protein foam "floats" on the wet water foam, accumulates organics from the watery foam beneath it, and is pushed up into the collection cup of a protein skimmer. An optimally adjusted and maintained protein skimmer collects only the dry protein foam and a small amount of the wet water foam.
http://bobbates.net/html/protein_skimmer_theory.html

or on some research related by Wilkens in TRA; Wilkens (1973) discusses two basic types of foam that develop in effective skimmers. The first layer of wet foam is referred to as "standard" scum and the second as "protein" scum. It is the second layer, the protein scum, that concentrates harmful organic substances from solution."...So if you foam is constantly wet - you're not pulling out the amount of organics that you should be.

I did see a couple of references to adjusting the skimmer temporarily to wet foam, after scraping the glass with an algae magnet - to better remove algae. Then adjusting it back to dry foam.

Can I get some clarification on this issue? Thanks!!!

[Spanky]

The first layer of wet foam is referred to as "standard" scum and the second as "protein" scum. It is the second layer, the protein scum, that concentrates harmful organic substances from solution."...So if you foam is constantly wet - you're not pulling out the amount of organics that you should be.

Now that makes a lot of sense, don't it.

Think about it, you have to let the wet foam concentrate in order to make the dry foam - or - just take it all out at one time.
The bigger advantage to wet foam is that it will take out more "particulate" matter and the organics associated with it. - detritus -

[tankgirl2]

Hi Spanky,
Thank you!! I trust your opinion (and mojoreef's opinion- he says the same thing).
Very confusing, though! Some of the sources said just the opposite - that dry foam has more particulate matter in it;
http://www.animalnetwork.com/fish2/a...ct/default.asp
"dry foam is richer in particulate matter than wet foam."

And, a whole bunch of discussions and articles stated that dry foam is richer in organics?
http://www.algone.com/protein_skimmer.htm
"Too much air injected will cause excess foam which will remove more water then DOC’s. This is referred to as “wet foam”. "

http://www.simplifiedreefkeeping.com/faq/skimmers.htm
"... probably a week or so before it starts to "kick in" and produce nice dry foam. A common mistake is to set the skimmer too high and that produces a wet foam. "

http://bobbates.net/html/protein_skimmer_theory.html
"An optimally adjusted and maintained protein skimmer collects only the dry protein foam and a small amount of the wet water foam. "

http://www.netpets.com/fish/reference/srab/srab5c.html
"Wet foam, mostly plain water, is not properly skimmed water, and contains much less of the organic and other elements we wish to remove, than a dry foam, that is heavily concentrated, dark in color, and thick. "

Then, too, I read that many proteins are clear (like egg whites) - so what's the dark stuff?
green, red and brown algae?
metal ions bound to proteins
phenols, phosphates, carbohydrates?

[Spanky]

This is without a doubt the hardest thing I've even had to explain - without using lots of hand motions! LOL

Yes dark, dry skimmate is more concentrated that wet skimmate. Because it takes longer for it to get concentrated?? Ok that didn't work, let me try that again.

Let's say you pass your water through the skimmer once every hour. It takes 12 hours to make dark concentrated skimmate, so your tank water has passed through the skimmer 12 times to remove that.
Then if you remove wet skimmate at the same volume you're removing more with each pass through the skimmer even though it's less concentrated.

Nope not there yet!

OK OK try this.

Even though you're removing wet skimmate and it's less concentrated than the dry, you're removing more things faster.

I give up!! can't do it. LOL ask Mike.

It's dark because it's organics and bacteria.

[gregt]

How about this? Wet = More = Better.

[galleon]

Originally posted by gregt
How about this? Wet = More = Better.

Wet = Faster Removal of crap = better


I know, I know, "Get back to work!"

[BuckWheat]

Riding the wave!

[BuckWheat]

Spanky, you sure it isn't ORP?

[BuckWheat]

[Spanky]

Nope, it's definitely OFR!

[wizardgus]

Let me try, I'll botch it up a bit, but you can fix it for me.

IIRC, the way a skimmer basically works is certain things are attracted to and adhere to the surface tension of the bubbles/foam. Not all things we want to remove from the water are equally attracted or as well attached. With a dry foam, those things less attracted are able to basically fall off before reaching the skimmer cup.

Hey, I'm a darn mechanic! Someone who understands science help me out here.

[BuckWheat]

Kool Man!

[mad_coder]

I'll try...
It shouldn't matter, ... in a perfect world your skimmer would remove the same total amount, say dry weight, of crud (for a better technical term) whether it's pulling out alot of water along with it or hardly any.

However, there's probably some loss of crud the longer it has to wait around to concentrate, which means if you want to remove the most crud, remove wet foam, and you'll get the most out (never all of it!)

[adrianleewelch]

this will sound stooopd but here goes, i ran the skimmer wet and then really dry for 12 hrs, i then took both types of the skimmed fluid and diluted them in 10 gallons of water, then i checked every available parameter on both, I believe that dry is better, as it had higher readings of the undesireables in it, I think if too wet then we get clean seawater making it to the collection cup, with not as much time for the undesireables to cling to bubbles, then no effective skimming is taking place, maby It would make a good study for some lab type ??

[gregt]

adrian,

Yes, if you make it TOO wet then all you are doing is a water change....