Alk falling but calcium

[cowlesdc]

I have been experiencing a consistent issue with my Alk falling and Calcium either rising or remaining elevated for several months. The issue began when I made the switch in my two part dosing from soda ash to sodium bicarbonate. I made the switch as I couldn’t keep my ph under 8.5 while dosing soda ash. I’m on well water and after I made the switch my ph has remained around 8.35, unless I go on vacation then it rises above 8.55.

here are my readings for the last 4 weeks.
5/10 - Alk-8.3 Ca-410 PH-8.37 - dosed additional soda ash after test to raise alk by .5
5/17- Alk-8.6 Ca- 433 PH- 8.33 - dosed additional soda ash after test to raise alk by .5
5/24- Alk-8.5 Ca- 478 PH - 8.38 - increased alk dosing
5/31- Alk-8.0 Ca- 459 PH - 8.38

I keep increasing my alk dosing, but my imbalance in dosing is getting close to 2alk/1Ca. Any ideas on how to get this imbalance under control?

Thanks

 

[Randy Holmes-Farley]

Welcome to Reef2Reef!

When you say you are on well water, are you using unpurified well water in the tank?

 

[cowlesdc]

Thanks for responding Randy. No, I have a RoDi system. I mentioned the well water as I thought it could be relevant. I should also mention that my salinity is currently at 37. I have tried to bring my levels down, but haven’t been able to. Any recommendations on how to bring my salinity down with out major effects to Alk and Ca? Again, thanks for the help.

 

[Randy Holmes-Farley]

Thanks for responding Randy. No, I have a RoDi system. I mentioned the well water as I thought it could be relevant. I should also mention that my salinity is currently at 37. I have tried to bring my levels down, but haven’t been able to. Any recommendations on how to bring my salinity down with out major effects to Alk and Ca? Again, thanks for the help.

No way to reduce salinity without reducing everything in it, but the effect isn't large. Everything will drop by a factor of 35/37 if you drop to 35 ppt, so by 0.946, or 459 ppm calcium to 434 ppm.

Take out some salt water each day and replace with fresh. You'll need to remove 5% of the tank water volume that way to get to 35 ppt.

For now, just supplement alk as needed. The calcium change may be due to salinity rising or test errors.

 

[cowlesdc]

Thanks for responding Randy. Isn’t this a losing battle with Alk though? As I try to lower the salinity I will need to add more Alk to try and keep it from plummeting, which In turn will increase salinity? Some of corals already look stressed and I really don’t want to lose anymore to this issue.

 

[Randy Holmes-Farley]

Thanks for responding Randy. Isn’t this a losing battle with Alk though? As I try to lower the salinity I will need to add more Alk to try and keep it from plummeting, which In turn will increase salinity? Some of corals already look stressed and I really don’t want to lose anymore to this issue.

No, it's an easy battle to win.

The alk drop from lowering salinity (only 8.0 dKH to 7.6 dKH for the whole salinity correction) is easily countered with a little baking soda.

 

[SlugSnorter]

Thanks for responding Randy. No, I have a RoDi system. I mentioned the well water as I thought it could be relevant. I should also mention that my salinity is currently at 37. I have tried to bring my levels down, but haven’t been able to. Any recommendations on how to bring my salinity down with out major effects to Alk and Ca? Again, thanks for the help.

Along with that Randy said, make sure that the output of your RODI system is 0 TDS too