dkh drops way to much

[Connor]

so I'm trying to get my water chemistry right. yesterday my calcium was 410 and my alkalinity was 9.1 dkh. today I tested the water and calcium was 430ppm and alkalinity was 7.0 dkh! why is my alkalinity dropping so fast? my calcium just increased. a week or two ago magneism was close to 1500 so I'm just natrally going to let that decrease over time. whats going on here?

 

[Downbeach]

The normal uptake of Alkalinity and Calcium is a ratio of about 50ppm(2.8dkh) of Alk to 20ppm of Ca (5:2). So, you should see a decline of Alk more quickly, and there is less in reserve in your system. This includes any abiotic precipitation too. A couple things that can appear to throw the readings off are water changes, using something other than RO/DI water for top off and WC's, i.e. tap water. Test kits and test proceedures can result in differences in readings as well.

 

[KritikaL]

double test.... might be a problem with test kit

 

[Randy Holmes-Farley Verified Community Expert]

What is in the tank?

Many tanks lose several dKH of alkinity per day, even an all soft coral tank may have enough coralline algae to lose 2 or even 3 dKH per day.

 

[Connor]

What is in the tank?

Many tanks lose several dKH of alkinity per day, even an all soft coral tank may have enough coralline algae to lose 2 or even 3 dKH per day.

NO coralline algae, one little montipora and that's my only sps right now, maybe 10 frags of lps and zoanthids

 

[Connor]

double test.... might be a problem with test kit

Well I have a red Sea test kit, but I'm not sure if I'm cleaning it correctly. First I just rinse it threw the sink then before I test I wash it out with tank water. Is that good enough?

 

[Randy Holmes-Farley Verified Community Expert]

Well, there's likely no "problem" that will be causing your alkalinity to drop. It is either being consumed in the tank by various normal processes (precipitation of calcium carbonate in corals, coralline algae, and abiotically on pumps etc. and as part of the nitrogen cycle, for example), or it is testing error.

If you get reasonable and reproducible values for alkalinity in some new salt water, then I'd just look to supplement the alkalinity to keep it where you want it. Baking soda dissolved in fresh water is a fine way in this sort of situation.

This calculator shows how much:

http://reef.diesyst.com/chemcalc/chem_calc3.html