2 part dosing

For me it was the other way around. Seemed like I always needed more alk than Calcium. And I constantly tweaked it that way for many years. Then I found an article which re-inforced the need for equal parts. I'll try to find it and post a link. I re-adjusted and have been dosing equal parts ever since. So, I support the equal parts recommendation.

That said, what test kits are you using? Are you confident that you are getting accurate results? If so, I would suggest trying a one time adjustment to get the calcium up to 420-425, and alk 8-9. Then try equal parts again.

 

Generally 2 part should be dosed at 1-1 ratio, calcium test kits have a large error range while alk is pretty accurate so it can be hard to tell how much calcium get used while alk is easy. I think the ratio is 20ppm calcium to 1 dkh alk used in tank.

What I have found that can really throw this off is what salt mix you are using. Often times they do not contain a balanced amount of ca/alk ratio. What salt do you use and have you tested the ca and alk of it? Some mixes are heavy ca and low alk or low alk and heavy ca, this can throw off the numbers with 2 part, but again remember most calcium tests are not very accurate. When I was using reef crystals, for example, some batches would test well over 500ppm ca, but around 10 alk - so dosing 1-1 2 part would make it look like I was adding too much calcium over time. Some people have the opposite problem with low ca and high alk.

The other thing I would l look at is the dosing pump calibration to make sure both are dosing the same amounts, and to make sure the solutions are correctly made.

 

Sounds good! Did the alk go from 8 to 11 over the course of 4 weeks? Any WC during that time? What is your daily alk consumption?

 

Hmmmm. So you were dosing the same amount daily and everything was holding fine with ca ~390 and alk ~8.5 and even after waterchanges it was pretty consistent there if I am reading correctly. Then it suddenly went from 9 to 11 in 2 days with no other changes to the tank? Did you do multiple tests to confirm? That is pretty strange for alk to increase that fast when everything was going smooth.

 

In my 75 gallon lps/sps tank I recently raised my daily dose to 36ml of Cal and Alk and 6 ml of Mag with a dosing pump. I had been at 32/32/6 I have added some corals that are growing well so my Alk has fallen to 142ppm/7.952 dKH. Hoping when I check today the Alk will be at 8.1ish and continue to rise. My calcium is consistently at 425-435 range no matter how much I change the dosing amount. My mag stays around 1290-1300. Rather than simplify it to much. This article always helped me understand the alk/cal interaction. http://www.reefkeeping.com/issues/2004-12/rhf/ Dont worry if your Cal is too low or high unless it appears extremely low. As long as the Alk is staying in an acceptable range the calcium will either slowly rise or you can add some supplemental to get to your comfortable range and then watch and see what the calcium does.

 

Oh and let me add that your lower calcium may be because you need to lower your 1:1 dosing amount. Lowering your dose of alkalinity and calcium will cause the calcium to be increased. It seems counter-intuitive to lower the calcium youre dosing along with the Alkalinity, but doing so has little change to the calcium in your tank. The real benefit is that because your ratios are apparently off, (Alk at 11 but 400cal), reducing the Alk will reduce demand for calcium and thus what IS dosed will begin to build up as the Alkalinity won't be consuming it at such a high rate. This is a very sloppy way to describe the interaction but I hope it makes sense. I would 1:1 dose 2 part in an amount that takes your alkalinity down to 9.5ish and you should see your calcium slowly rise up towards 425ish as there is less alkalinity to consume it, even though you're reducing the calcium dosed.