High KH - a problem in FOWLR?

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Carissa

Aquarium Advice Apprentice
Joined
Sep 20, 2008
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I'm wondering if there is any problem if my KH is between 18 - 22 degrees. I know that this can lower calcium levels, but with no corals, does it really matter? I've posted everywhere and researched it, and can't get a definitive answer. Also would this affect coralline algae? If so, would adding CaCl help?
 
As far as fish go, I'm not sure about the effects of high alkalinity on them. I'd guess they wouldn't like it since it's not normal for saltwater to be that high. But if it's bad for their health... I have no clue.

Regarding coralline algae... that high of alk probably would cause issues, indirectly. Have you measured your Ca levels? As you mentioned, I'd guess they're pretty low because of your high alk. And without proper levels of Ca (greater than 360 or so) you aren't going to have much growth, if any. When I first started my tank, my coralline growth outpaced the Ca replenishment from my water changes and when my Ca dropped below about 340, my coralline algae started turning white.

I don't think adding calcium will help. With that high of alkalinity, you'd most likely precipitate it out immediately and cause a little snow storm in your tank.

How'd the alk get that high? Weekly water changes will eventually bring those levels back down to where they should be.
 
I was thinking that adding Ca would remove some of the alkalinity, and eventually get to a point where it wouldn't precipitate out anymore.
 
Just doing water changes (without doing any dosing of any other supplements) would probably be a more controlled way of reducing your alkalinity.
 
I'm not trying to reduce it. I was just wondering if it would cause any problems with a future tank as I have well water. What level does calcium need to be at to be good for coralline algae growth?
 
Hey, does anyone have a definitive answer on the original question? I too did a pile of research and can't find anything that tells me what bad things happen when the alkalinity is too high. I can find several opinions on the proper range, and how to raise it, but not much on how to lower it (other than water changes) and nothing on why it's bad to have it too high.
 
Hey, does anyone have a definitive answer on the original question?
You will find there are very few "definite" answers in this hobby. Definite answers require research, which requires money and there isn't a whole lot of money being put into marine aquaria research.
There are issues with high alk, but it mostly involves corals/calcification. To begin with, there is no way alk is 18-22 dKH without adding lots of buffer. If buffers are being added to raise pH, this is a common problem. Buffers won't keep pH up, but will continually build up alk. What salt are you using?
The easiest way to lower alk is do water changes with unbuffered saltwater. No salt mixes to an alk level that high.

A Simplified Guide to the Relationship Between Calcium, Alkalinity, Magnesium and pH
Calcium and Alkalinity Balance Issues
 
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