Recommended alkalinity??

[Mrspit66]

Hi, guys. Hope you can help me out. I'm really confused about alkalinity. One LFS said if you want corals, it needs to be between 7 and 10. That sounds crazy to me. Everything else I'm reading says 2.5 - 5 is acceptable, with 3 to 3.5 being pretty much ideal. Help, please! I don't have any corals except a couple of mushrooms right now, but I do plan on having more eventually.

Thanks!!

Cathy

[Randy Holmes-Farley]

Cathy:

You are experiencing one of the most irritating problems in this hobby: unit confusion.

There are a variety of different units that describe alkalinity.

I usually recommend that alkalinity be kept at 2.5 to 4 meq/L, or 7-11 dKH. I won't even tell you what that is in ppm, but you can read all about alkalinity, what it is, what it's units mean, etc. in this article:

http://www.advancedaquarist.com/issu.../chemistry.htm

[Mrspit66]

Thanks, Randy. You're exactly right. There was unit confusion. I thought I had already printed out your article, but I don't guess I did before. It's printing now even as I write!!

BTW, my pH is about 8.3 and CA is about 400 and alk about 2.5 meg/L! Looking in good shape! Hoping I can keep it there!! ;o)

Cathy

[kstagg]

Randy Holmes-Farley,

I agree on the alkalinity of 2.5-4.0. My question now is, what level do you recommend for calcium levels. I understand that NSW is between 390 to 410. After reading on this forum, I have been keeping mine around 425-450. But I don't want to add more than can possibly be used. It seems the higher the level the faster the dissipation or fall. If it a waste to get past NSW levels then I will slowly lower my calcium levels.

Any help would be greatly appreciated. I wrote a while back that I thought there was nothing you didn't know. Please understand that that was as far as chemistry was related, I don't know about anything else. I do appreciate you and have learned much from your writings.

Thanks from all of us, Keith

ps. is 2.5-4.0 meq/L in total alkalinity or carbonate alkalinity?

[Randy Holmes-Farley]

Keith:

This article outlines some of the reasons for wanting alkalinity to be above natural levels, but not calcium:

http://www.advancedaquarist.com/issues/apr2002/chem.htm

In short, calcification by corals appears to be increased by increased alkalinity.

OTOH, calcification is only impacted by calcium levels when it drops below natural levels (where calcification declines).

These results are based on few studies, and better studies on more organsims might give a different picture, but that's what's available now.

Personally, I'd let the calcium level drop, but it is probably not hurting anything.


I do appreciate you and have learned much from your writings.

Thanks

[kstagg]

I edited my post but you beat me to the punch.

Here is my last question for the night:

Is 2.5-4.0 meq/L in total alkalinity or carbonate alkalinity and do you shoot for the middle, upper, or lower of the range.

I will also let my calcium drop to the 390 to 400 range.

Thanks again, Keith

[Randy Holmes-Farley]

It can be either!

Actually, it should be the alkalinity coming from bicarbonate and carbonate. Some people call this carbonate alkalinity (some use a different definition for carbonate alkalinity: the alkalinity from carbonate alone, that's why I make the distinction).

In normal seawater, the bicarbonate and carbonate will comprise nearly all of the alkalinity, and 2.5 to 4 meq/l alkalinity applies just as well to total alkalinity under those circumstances.

If, however, the salt mix is greatly skewed with other buffers (like Seachem salt is with borate) then total alkalinity must be much higher than 2.5 to 4 meq/L.