Ca reactor - high alk., low Ca

[euphylius]

I have Ca reactor with crushed corals. After two months I am getting next parameters:
- water 17 kH, 340 Ca
- reactor output 44,5 kH 440 Ca

There is difference 27,5 kH and only 100 mg/l Ca.

Do you have any idea why that would happen?

[euphylius]

I forgot to mention, I am also using some white sand to increase Mg in reactor. Can this be the source?

And a last question. Can open fireplace have CO2 – alk. influence?

[Randy Holmes-Farley]

Yes, that can certainly be the problem (if the calcium and alkalinity were previously in balance; if not, perhaps you just need to add calcium chloride and back off the reactor; see the second link below for more details).

You cannot raise magneisum in that way without alkalinity getting too high. I address that concern in this article:

Magnesium
http://www.advancedaquarist.com/issues/oct2003/chem.htm


from it:

"It has been suggested that adding dolomite to CaCO3/CO2 reactors can help with magnesium problems. Dolomite is a material that contains both magnesium and calcium carbonate. If dolomite is being added to the reactor to maintain existing appropriate magnesium levels against the continual depletion via calcification (for example, if the calcium carbonate being used is too low in magnesium to maintain adequate magnesium) then this is a fine approach.

However, this method is unsuitable if the goal is to raise magnesium levels. The problem is that for every magnesium ion released from the dolomite, 2 units of alkalinity are also released:

MgCO3 ----> Mg++ + CO3--

Consequently, if one wants to raise magnesium by 100 ppm, the alkalinity will necessarily rise by 8.2 meq/L (23 dKH). The only way around this problem is to add a mineral acid (not vinegar) to the aquarium to reduce the alkalinity, and that may be more problematic than just adding magnesium in the first place."


To fix this problem, you need to add calcium via calcum chloride, and remove the dolomite from the reactor. This article will help:

Solving Calcium and Alkalinity Problems
http://www.advancedaquarist.com/issues/nov2002/chem.htm

[euphylius]

A friend of my has made several tests ( http://www.sloreef.com/bojan/Ca1.xls ), when he was tuning CaCO3/CO2 reactor. In cases, where we can calculate reactor coefficient,

c= (Ca output – Ca input) / (dKH output – dKH input),

there are interesting results. Coefficient varies from 5.42 to 8.59. Before adding dolomite I had 400 Ca and 12 dKH. I suppose my coefficient was below than normal 7. After adding dolomite everything went only worse.

[Randy Holmes-Farley]

What do you use that coefficient for? I'm surprised that it varies that much (in the absence of using things like dolomite in the reactor).

[euphylius]

I want to validate if reactor is producing normal 7 ppm Ca / 1 dKH. In my case it seems that reactor was producing more alkalinity than Ca. Is this possible? Can improper reactor balance - ph, flow… cause that? From that sheet I calculated that coefficient to see if that is true, where data were available. I think coefficient shows that very good. I would call that Reactor Efficient Coefficient.

[Randy Holmes-Farley]

Can improper reactor balance - ph, flow… cause that?

No. The only things that can cause that are measurement errors, or having something other than pure calcium carbonate in the reactor.

[euphylius]

Thank you for response.

I assume an Aquarium Systems crushed coral is OK.

[Randy Holmes-Farley]

Assuming that it actually is crushed coral of an appropriate size, it should be fine. :)