Protein Skimmers & KH/Alkalinity

[acropora1981]

Has anyone ever heard of protein skimming reducing KH or alkalinity? I just had a heated debate with a fellow who is absolutely convinced that protein skimming reduces alkalinity, but I've not heard of this in my 15 yrs of reef keeping.

[Randy Holmes-Farley]

No, skimmers cannot reduce alkalinity.

They may remove other things that could allows corals and coralline algae to calcify faster, thereby reducing alkalinity, so that could be a basis for his statement, even if not accurate.

[acropora1981]

Originally Posted by Randy Holmes-Farley

No, skimmers cannot reduce alkalinity.

They may remove other things that could allows corals and coralline algae to calcify faster, thereby reducing alkalinity, so that could be a basis for his statement, even if not accurate.

Thanks Randy. My response to him was that in my 15 years I had not read anything of the sort, that I couldn't see how it could happen that way, and that yes, its entirely possible for your KH to go from 10 to 8 in 3 days if you have a good amount of corals. He wouldn't budge. "You fellas all looove yer protein skimmers. Those damn things make my KH crash out and bring down the ph!"

Then I went into how skimmer raise pH via off gassing of CO2, but he wasnt interested in that.... TY for confirmation.

[bobbychullo]

i've read they will remove calcium from the water but not KH/Alk. you can do a search on the internet, someone tested it. iirc, depending on how wet you skim, it pulled out a good amount of calcium.

[Randy Holmes-Farley]

Skimmers don't remove soluble calcium appreciably more than is already present in the tank water that the skimmate contains (which, of course, contains 300-600 ppm calcium), but skimmers can remove calcium carbonate particulates (like stirred up fine sand, tiny suspended creatures with calcium carbonate skeletons, etc.).

[rkaires]

Hey Randy,

What is you take on needle wheel skimmers removing or depleting K+ form the water. I've often seen this debated on other forums.

Thanks,

[Randy Holmes-Farley]

Potassium itself in the water cannot be skimmed out with any type of skimmer.

Whole bacteria can be skimmed out with all of whatever is inside of them, including potassium. Many bacteria tend to have higher internal than external potassium concentrations. So skimmed bacteria could take out some potassium relative to sodium.

Experimentally, Ron Shimek did not find potassium to be elevated in skimmate relative to seawater, and the skimmer sludge was only slightly elevated in potassium:

http://reefkeeping.com/issues/2002-1...ture/index.php

[rkaires]

Thank you,

[Randy Holmes-Farley]

Sure thing.

I would add one additional point.

Folks should not assume that organic carbon dosing necessarily results in depletion of potassium by this route. That is because foods that come into the tank also have potassium elevated relative to tank water because they are made of cells that sequester potassium inside of them just as bacteria (or macroalgae) used for export may remove potassium. In fact, foods may have a higher potassium to sodium ratio than does skimmate or skimmer sludge based on tests like Ron Shimek’s food and skimmate studies.

http://replay.waybackmachine.org/200...data/foods.asp

So overall, one might get a balance, and that seems what a number of studies have shown. Ron's data on tanks, for example, or my own data for my tank with heavy organic carbon dosing and no apparent depletion of potassium.

The one thing that is a potential potassium depleter is zeolite use by zeovit users. The zeolite itself may bind potassium from the water, in addition to any export by bacteria (on the media, by skimming, etc).

[bobbychullo]

thanks for clearing that up

[Randy Holmes-Farley]

Happy Reefing.

[rkaires]

Originally Posted by Randy Holmes-Farley

Sure thing.

I would add one additional point.

Folks should not assume that organic carbon dosing necessarily results in depletion of potassium by this route. That is because foods that come into the tank also have potassium elevated relative to tank water because they are made of cells that sequester potassium inside of them just as bacteria (or macroalgae) used for export may remove potassium. In fact, foods may have a higher potassium to sodium ratio than does skimmate or skimmer sludge based on tests like Ron Shimek’s food and skimmate studies.

http://replay.waybackmachine.org/200...data/foods.asp

So overall, one might get a balance, and that seems what a number of studies have shown. Ron's data on tanks, for example, or my own data for my tank with heavy organic carbon dosing and no apparent depletion of potassium.

The one thing that is a potential potassium depleter is zeolite use by zeovit users. The zeolite itself may bind potassium from the water, in addition to any export by bacteria (on the media, by skimming, etc).

Great info Randy!

Thanks,