Montipora digitata reaction to high alk+ca

[zenya]

Hi Randy,

After I exchanged my CO2 bottle and replaced media in my calcium reactor I had to redial it and adjusted to the numbers pretty close as before. In the past few days I've noticed that all of my M.digitatas have very little in the way of polyps extension and don't look quite as "happy" as before.So I started running tests and the only values that were out of the norm(previous values) were calcium and alkalinty wich are 16dkh and 520ppm respectively. No PO4 or NO2,the same for NH4 and only trace of NO3.
FWIW, the Acroporas don't look affected at all and neither the other inverts or the fish. Oh,the PH is 8.0 at night and about 8.2-8.3 during lights on.
The only other change was the w/change(2nd) of 5gal. with CS bio-mix.
My question is should I just dial down my reactor or shut it down completely?
Is there any other way of lowering alkalinity without impacting PH?I'm not sure if I can supersaturate with calcium chloride at this point to bring alkalinty down without negative effects.

TIA.

PS. I know it's a stupid question but what is the difference between ppm and meg/l when you describe calcium values,if any.I was asked this question and was stumped to my shamehttp://smilies.sofrayt.com/%5E/k/sorry.gif

[Randy Holmes-Farley]

I would think that if you dial the reactor back a bit by using less CO2, then the calcium and alk will drop a bit (or not rise as much) and the pH may not drop (nor get too high). So that would be my suggestion.

OTOH, I've not heard of any instance where calcium and alkalinity values like yours caused a problem with corals. So I don't know if that is the explanation, or something else.

Rarely do aquarists use meq/L (milliequivalents per liter) when referring to calcium. The meaning is actually even ambiguous since 1 calcium atom might be providing 1 equivalent or 2 equivalents, depending on what exactly one is talking about. 1 mM calcium is 40 ppm.

More often, people use ppm, meq/L and dKH for alkalinity. These are all mathematically related, and the origin and relationships between these units are discussed at the end of this article on alkalinity:

http://www.advancedaquarist.com/issues/feb2002/chemistry.htm

[zenya]

Thanks a bunch,Randy. I'll just dial it down then and let it come down on its own.
If you don't mind, I'll just copy and paste your response about the ppm and meg/l explanation,no way I'll remember everything :)
FWIW, I'm not sure why it is happening and it very well might be coincidental but I had two Acropora colonies bleach after the second 5gal. water change with the CS salt.They are recovering though and they were also W.Smith colonies , none of the colonies grown from frags were affected

http://smilies.sofrayt.com/%5E/_950/upset.gif

[Randy Holmes-Farley]

If you don't mind, I'll just copy and paste your response about the ppm and meg/l explanation,no way I'll remember everything

Sure.

I had two Acropora colonies bleach after the second 5gal. water change with the CS salt.

Well, at least you are not alone with such a problem.:(