Calcium Reactor Principles

[CarlosS]

Guys:

Some days ago I was in a meeting with some reef aquarium partners. We were talking about calcium reactors and there was a topic that I need to be clarified.

While the reactor chamber is bigger, the DKH is higher?

Some months ago I could see that the calcium media was depleted and when I meassured alkalinity it was 20ºDKH. I filled the reactor to the top and 24 hours later I meassured again and DKH was 28. That means while reactor chamber is bigger DKH is higher, or not? Or while more reactor media, more alkalinity.

I am specting that because I feel that mi old calcium reactor is small for my system, a Geo 612 for 195 gals. I bought a Geo 624 and I suppose that DKH will be higher than my old Geo 612.

Am I right? or Am I confused?

[Randy Holmes-Farley]

More media (as in a larger reactor) may allow higher dKH with a fixed flow rate, or the same dKH at a faster flow rate due to higher surface area of media, hence allowing more/faster dissolution at the same pH.

But in general, people with larger reactor do not run them at a higher dKH. They would run them at a similar dKH with a higher flow rate, so delivering more calcium and alkalinity to the tank (and using more CO2 as well).

This article has more:

A Guide to Using Calcium Reactors
http://www.reefkeeping.com/issues/2002-05/sh/feature/index.php

[CarlosS]

Yes Randy, you are right. Thanks a lot for your comment

My big problem was that I had to run my calcium reactor with very low ph (6.4) and high flow rate (efluent), that means more available CO2 to the tank. This for keeping calcium and alkalinity at high values.

With a bigger reactor I could decrease the efluent, keeping the same dkh, and delivering less CO2 to the tank.

[Randy Holmes-Farley]

Sounds good.

Happy Reefing. :)

[CarlosS]

Thanks Randy.

Another question:

I tested efluent and I got 0.2-0.5 ppm of phosphate. It is this normal?

I am using ARM Coarse (CaribSea), and Gen-X reactor media and some rocks of Dolomite.

[Randy Holmes-Farley]

Seems pretty high, but reactor media do often have phosphate in them.

Did you test the tank water?

[CarlosS]

Randy:

The tank water is 0 ppm. Tested with Seachem

[Randy Holmes-Farley]

What media?

[CarlosS]

Randy:

I am using 16 pounds of Gen-X (Pacific Coast), 4 pounds of ARM Coarse (Caribsea) and some small pieces of Dolomite.

[Randy Holmes-Farley]

I've not heard anything specific about the Gen-X media. Greg Hiller discusses phosphate in media here, and shows data for at least one grade of Caribsea material:

http://www.advancedaquarist.com/issues/april2003/short.htm

[CarlosS]

Thank you very much for your comments.

Checking that link, I wouldn't have to worry about my levels. Greg Hiller talks about 2.0 ppm, and I just have 0.2, I am great.

I am currently using rowaphos to control this levels of phosphate, but would you recommend connect the efluent of the calcium reactor directly to the intake of the phosphate reactor?.

[das75]

Randy, not to go totally of topic here but can you comment on the accuracy of hobby test kits (Seachem, Salifert etc) for measuring phosphate?

[Randy Holmes-Farley]

I've not tested any to really say, but I expect the biggest errors, proportionally anyway) are at the low end, where most of us are focussed.

I've only tested the Hach PO-19 phosphate kit, and it is reasonably accurate down to its limit of detection, which is about 0.03 ppm, maybe 0..02 ppm if you have patience and good eyes. :)