Dropping Alk but Ca not budging with Kalk ATO dosing.

[Bradley Keck]

Hey everyone! Hope all your reefs are looking good for the Holidays! I'm just glad I actually have a tank up and running this Christmas! I am in need of a little advice as I am now facing the new challenge of parameter stability with coral growth getting under way. I have a 150g mixed reef that is 18weeks old now. Currently I have 3 softies, 8 LPS, and 8 SPS. Seeing growth primarily on my SPS particulary my Monti's and birds nest. LPS are slow going, but a little growth on one acan and my trumpet. Everything is doing well overall. I test all parameters weekly and do 30g WC every two weeks. I started dosing Kalk through my ATO at the end of October when I firs t detected dropping levels of Ca and Alk. Prior to the end of October, I was consistently:
Salinity= 1.025
ph 8.1 to 8.2
Alk 8.1
Ca 430-470
Mg 1320-1350
I started dosing when my Ca hit 420 and Alk read 7.8. I started with 1/2tsp/gallon RODI. Alk went to 8.1 and Ca 480. I continued to dose in this fashion until I got an Alk reading in mid-November of 8.5, but Ca was 425. The next week Ca hit all time low of 390 and Alk all time high of 8.5. I decided to back off adding Kalk. After a week Ca was 450 and Alk down to 8.4. Today I am due for WC and took some readings before hand. Had a complete reversal. Alk 7.8 and Ca 475. Now, I stopped adding Kalk two weeks ago, but I continued to refill my ATO and of course with all the slurry in the bottom, it would mix up some leftover Kalk, so I think some Kalk was still being dosed over the past two weeks. Could it be the Ca was more potent than the Alk with what had settled in the bottom of the ATO or is that not possible? For those of you that use kalk in your ATO, do just keep adding more Kalk and don't worry about what leftover slurry gets stirred up when you add more RODI? Could this not even be part of the problem and I need to just switch to 2 part? I decided to go the Kalk route to avoid additional equipment or manual dosing. I don't want to get cacught up in chasing numbers, but I feel like these swings of the two going opposite directions is going to catch up to me. Mg has been solid and I have not had it drop below 1320. Sorry so many questions, but I'm not sure why I am seeing the two yo-yo in opposite directions when I'm dosing Kalk. It's like the corals and coraline are using all Alk sometimes and Ca others.

 

[Bradley Keck]

My latest swing from last week to this week was as follows:
12/7
salinity 1.025
ph 8.23
Alk 8.4
Phos 0
Nitrate 0
Ca 450
Mg 1360

12/14
Salinity 1.025
ph 8.37
Alk 7.8
Phos .02
Nitrate 0
Ca 475
Mg 1320

I know I know. My Nitrates need raised. I'm working on it through using reef chili more often and feeding generously. My phos will vary from o.o to .o2 depending on the week

 

[Bradley Keck]

Bump

 

[lapin]

I have noticed in all my new tanks, alk is the first thing that drops as everything starts to grow. To fix this I use a higher alk salt mix and change water more often. To bring alk up to the level I wanted, I used Randys baked baking soda. To keep it there I mix equal parts Red Sea Blue bucket with Red Sea Coral Pro salt. As my corals start using more alk I can use more pro than regular to keep my alk where I want it.
note: my current tank is now 10 months old

 

[Bradley Keck]

Good to know this can be normal for newly establishing corals. I guess I just assumed Alk and Ca would go up and down together. I'm using HW Marine reefer salt which is higher in Alk. I did a WC after taking those last numbers, and Alk was up to 8.1 which is right in the most consistent range I have measured in the last 4 months (8.1-8.2). Ca was 450 and Mg 1360. Spot on numbers. It's funny you suggested WC, because I thought after taking measures before and after a WC, maybe I should just increase WC to 1x/wk and maybe only do 20g. That might help keep my numbers from fluctuating so much right now. I would like to eventually be able to do WC every two weeks, or even once a month. I just do not have this Kalk dosing through the ATO figured out. The recommendations from BRS are low demand 1/2tsp per 1 gallon RODI. I dosed 1/2 that. There is always a thick slurry at the bottom even after not adding any Kalk for over a week. So when I fill the ATO(2-4 g every couple of days), it stirs it up again, and so I'm thinking it's still dosing some Kalk, but maybe not? I made sure to build a good WC station before I got my tank up and running, so maybe it's time to start using it more often and not have to worry about the Kalk dosing right now. Thank You for your help.

 

[Retro Reefer]

I would add your Kalkwasser independently with a reactor, dosing pump or the old school drip method using ATO is going to cause fluctuations in amounts being added to your tank and your tank is very young so it probably hasn’t fully stabilized yet as well..

 

[Randy Holmes-Farley Verified Community Expert]

Most often such short term imbalances are simply test error or changes from a water change..

Unless you are dropping nitrate at a substantial rate (which adds alkalinity), there is also no situation where calcium declines but alkalinity does not, aside from dosing calcium and not alkalinity.

 

[Bradley Keck]

I have thought about that. My goal during set-up was to have as little stuff as possible, and I liked the idea of just adding it to the ATO, but it only makes sense that the Kalk is being added based on evaporation rate not a dosing rate. I thought maybe I could adjust for that by reducing the potency/concentration of Kalk, but so far it's not working to stabilize my numbers b/t WC's. I checked out some kalk reactors and DIY kits, etc. and thought I would try the ATO way first and if I ran into troubles, go the reactor route. Thing is, I am not sure how much of this is being a new tank. Maybe the fact I have had Ca go from 390 to 475 in a 3 week period and alk go from 8.5 to 7.8 in a three week period means it's just new tank swings and not the Kalk dosing?

 

[Bradley Keck]

That's what I was wondering! I didn't think it made sense for one to go up and the other down. Thank You Randy! The readings over the past three weeks I question is the 390 I had in Ca when Alk was 8.4 and then the Alk reading of 7.8 when Ca was 475. Otherwise, I have been able to keep things around 8.1-8.3 and 440-470. With my corals are all doing well with some growth, mostly on my SPS, and good polyp extension I gotta think I am keeping things fairly stable in this delicate and unstable first year time period. Thanks Again!

 

[Randy Holmes-Farley Verified Community Expert]

Maybe the fact I have had Ca go from 390 to 475 in a 3 week period and alk go from 8.5 to 7.8 in a three week period means it's just new tank swings and not the Kalk dosing?

Focus on the alkalinty. It looks quite stable to me. It is a far better measure of whether you are dosing an appropriate amount. Just ignore the calcium unless it gets so low that you need to dose some (unlikely, limewater/kalkwasser actually very slowly overdoses calcium relative to alkalinity so if you maintain alk, calcium will very slowly rise).

As I stated, I expect the calcium change is mostly test error. The real consumption of calcium if alk declined by 0.7 dKH is only about 5 ppm.

 

[theMeat]

My first guess for swings like that would be magnesium is low, but your tests shows it’s not.
My second guess would be some pumps are on timer on/off at night or something?

 

[Bradley Keck]

Thank You. I will focus on Alk, and adjust how I am keeping it where I want it. Glad to hear that it relatively stable. Thank you. Always very helpful.