wet skim v's dry skim

[JMartin104]

How much do your skimmers remove? Mine takes out 1/4 cup at most per week. I'd never worry about that for SG. BTW, my skimmate is pretty clear. Unless my tank is really nasty, I don't get the thick green stuff -- not like I did in the beginning anyway.

 

[Palting]

I do about 600-700 cc's a week. Pic below is about 5 days worth.

 

[d0ughb0y]

Will it though? (this is a serious question). I am not personally certain a dry skim is "using" more air than a wet skim.

you produce wet skim either by increasing water level (by restricting the skimmer output or actually raising the sump water level), or by covering the air intake hose. wet skim is a result of reduced air intake.

 

[bobbychullo]

an analysis of what exactly is in skimmate:

http://www.advancedaquarist.com/2010/2/aafeature

 

[bobbychullo]

i notice my water is much clearer the wetter i skim. i do weekly water changes to maintain proper salinity, i haven't much of a problem so far. i clean my skimmer cup nightly.

 

[evsalty]

Thanks for that ev. I wonder if they actually gathered real data to come up with that conclusion.

That I can not answer. I can say that they did lots and lots of testing for performance with various pumps and give you several pumps as recommendations for use on their skimmers based on the amount of skim they saw during testing. They even go as far as trying out overdriving sized pumps for each skimmer. On the other hand they have not changed their designs in over half a decade so I don't know what to make of that lol.

you produce wet skim either by increasing water level (by restricting the skimmer output or actually raising the sump water level), or by covering the air intake hose. wet skim is a result of reduced air intake.

HMMM. When you raise or lower the water level inside your skimmer all you are doing is setting the distance the foam has to travel to get into the cup. When you set the water level high there is lees distance for the bubbles to travel so they are still very wet and bring the water over the edge into the cup with them. When the water level is lower the bubbles have to travel further and thus start to shed off some of the water. If too far down then the bubbles will break before they even have a chance to get into the cup. This is assuming no change to the air adjustment ofcorse. The amount of air will only change if you actually adjust the air intake as the air intake is above the water line.

 

[heller792]

Im onboard with the fact that they pull the same amount (maybe). But if you wet skimm then your removing it from the sytem quicker so its not having any adverse effects on the system and its contained in the skimmer cup. If you dry skimm then it takes longer to catch and spends more time in the system. Does this make sence?

Dave

 

[lordofthereef]

Im onboard with the fact that they pull the same amount (maybe). But if you wet skimm then your removing it from the sytem quicker so its not having any adverse effects on the system and its contained in the skimmer cup. If you dry skimm then it takes longer to catch and spends more time in the system. Does this make sence?

If this is the case (and I personally don't have any knowledge poiting to it not being so), then what is the sweet spot. In other words, I wonder where the equilibrium point is. If wet skimming is "faster", but over time, both methods are equal, there has to be an equilibrium point measured in time.

 

[Randy Holmes-Farley]

IMO, there are too many different ways to generate a wet vs a dry foam to say anything definitive.

That said, if all you do to a wet foam is allow more draining to form a dry foam, then there is no way that the dry foam can contain more organic matter than the wet foam it came from, and if any organic matter drains away with the draining water (as some likely will), then the wet foam must contain more organics.

 

[heller792]

thanks gents

 

[lordofthereef]

Randy,
I am not sure I understand how you are using the term "draining" here.

 

[heller792]

does he mean add a small drain hole in the skimmer so the gunk stays in the cup?

 

[Randy Holmes-Farley]

I mean that how a skimmer works is to generate a wet foam, and then the water between the bubbles is allowed to drain out, leaving behind the bubble surfaces which are coated with organics. That water drains back to the tank by descending the skimmer column, not draining into the collection cup.

So making a wet foam is the first step, and draining out water is the way it is made more dry. The more draining, the dryer it is.

i discuss such processes here:


What is Skimming?
http://reefkeeping.com/issues/2006-08/rhf/index.php


from it:

Foam Formation and Draining

Once a skimmer contains a large number of bubbles coated with organics, it is necessary to somehow remove the bubble surfaces, but not the majority of the water nearby. This is most easily accomplished by allowing the bubbles to form a foam. Foam formation takes place when bubbles accumulate and interact. The froth of bubbles begins to drain under gravity, removing much of the water between the bubbles. Some of the bubbles merge into larger bubbles. As long as the bubbles do not pop before significant draining occurs, then the organics will be left behind in the foam, along with some residual water. Eventually, the concentration of organics on the top of the foam becomes great enough that they exceed the solubility limit, and small particulates of organics form. These particulates are generally what a skimmer collects, along with some water and organics that remain present in solution or at the air/water interface.