Testing results and some ?

[graveyardworm]

A month ago I started something I should've started years ago, regular weekly testing, but my tank was small and demand was low so with regular water changes and occasional testing everything was fine. Now my system is larger and demands have changed so i figured it was time, and I'd like to post my results, and ask for some dosing tips. All tests are Salifert

Switched to TM Pro results of salt mix tests
SG - 35 ppt
NO3 - und
PO4 - und
CA - slightly over 500
Mg - 1175
Alk - 2.63 meg/l

Tank params 3-4-06
SG - 35 ppt
NO3 - 2.5 ppm
PO4 - und
Ca - 440 ppm
Mg - 1170
Alk - 2.74 meg/l

3-13-06
SG - 35 ppt
NO3 - 5 ppm
Ca - 450 ppm
Mg - 1170 ppm
Alk - 2.58

3-25-06
Sg - 35ppt
NO3 - 5 ppm
Si - und
PO4 - und
Ca - 450
Mg - 1140
Alk - 2.51

4-2-06
NO3 - 4ppm
Sg - 35ppt
Ca - 480
Mg - 1125
Alk - 2.51

So my testing has established some trends, my Ca is going up which I would expect my tank is soft coral dominated with just a couple stony corals ( coraline has really taken off with switch to TM Pro ). Mg is on its way down, about two weeks ago I added a mangrove which has exceptional root growth since it was added I'm not sure how much Mg a single mangrove might use, but the drop seems significant considering I've changed over 100 gals water in the last month. Finally the Alk has been on a steady decline, I can only attribute this to the various macros I've added in the last couple months, I have a feeling they're using it as a carbon source.

So now I need to dose to bring my Mg and Alk up, I'll be using Randy's improved method, I already have the Mag flake, and I'll be getting epsom salt and baking soda today.

I've been following a thread in the macro forum about CO2 dosing for macros. Would this help reduce demand for my carbonate (alk), and could there be any adverse impacts to corals? I could dose it directly to my fuge so it would take a minute for it to get to my display, the fuge drains into my sump and my seagrass tank first.

 

[Randy Holmes-Farley]

Are you doing any water changes in this time?

I personally do not believe that mangroves in a reef tank are a significant sink for magnesium.

Macroalgae do not reduce alkalinity unless they are calcifying (like Halimeda). When the use bicarbonate as a carbon source, they leave the alkalinity behind:

HCO3- ---> CO3 (which they use) + OH- (which they do not)

You have added nothing to supply calcium and alkalinity so far?
I would not dose CO2. I do not think it generally useful, unless the pH is too high.

 

[graveyardworm]

Thank you for reply, yes I have changed around 125 gals during this time frame. I thought I read somewhere that all plants use carbon which they take from CO2 or in the case of macros they can take it from carbonate if CO2 is limited. Typically I dont check PH frequently as it has always been at 8.2 when I test (Red sea kit). Eventually I'll get a pinpoint PH monitor.

edit: no I havent been dosing CA or Alk, I have however been dosing iron @ 5ml per day, undetectable on seachem kit. I have also been maintaining NO3 @ 5 ppm with KNO3 dosing as needed. Last night I started with Iodine dosing @ 4ml, which I was going to continue daily. Total system gals is alittle over 300.

 

[Randy Holmes-Farley]

Then I expect the calcium drift is from the water changes. If you plan to continue that much water changing, then perhaps all you need (at least until the demand rises) is to maintain alkalinity with baking soda.

This calculator shows how much to use:

Reef Chemicals Calculator
http://home.comcast.net/~jdieck1/chem_calc3.html