Should there be a ratio between calcium and Alkalinity

[Miami Reef]

I add 70ml each of BRS 2 part soda ash and calcium chloride with auto doser daily. It’s been dosing that amount for 2 weeks and I haven’t had the need to adjust dosage because levels are spot on the dot.

Alk is 9.1dkh
Calcium is 420. I used salifert and Red Sea. Same results.

I really expected myself to need to raise my dosage by now. I also expected that my calcium would be higher in a higher ratio to alk at 9dkh. I commonly see calcium of 420 be in ratio of alk at 7-8dkh.

 

[homer1475]

Ever see this calc?

Reef Chemistry Calculator

Punch in your ALK numbers, and it will tell you what balanced calcium should be. Doesn't matter though as long as you keep them in range and stable.

For a DKH of 9.1, 426ppm of calcium is balanced. Have fun trying to test that though. lol

 

[Randy Holmes-Farley Verified Community Expert]

I add 70ml each of BRS 2 part soda ash and calcium chloride with auto doser daily. It’s been dosing that amount for 2 weeks and I haven’t had the need to adjust dosage because levels are spot on the dot.

Alk is 9.1dkh
Calcium is 420. I used salifert and Red Sea. Same results.

I really expected myself to need to raise my dosage by now. I also expected that my calcium would be higher in a higher ratio to alk at 9dkh. I commonly see calcium of 420 be in ratio of alk at 7-8dkh.

I do not think ratios are that useful for alk and calcium. The number you show 7/420 is about the ratio in natural seawater (it's actually a little lower in alk, but folks round it to 7 dKH), not a target ratio.

Corals are not very sensitive to the calcium level, as long as there is enough, since it is not a rate limiting material. If you are in the 400-550 ppm range, it likely doesn't matter much what the value is.

Alkalinity, on the other hand, is often a rate limiting material for skeletal growth, and alk changes impact how corals grow.

 

[Tamberav]

I stopped testing for calcium a year or so ago. It was always a desirable range when dosing 2 part and it just seemed like a waste of time/money. I still test Alk ofc.

 

[Miami Reef]

I stopped testing for calcium a year or so ago. It was always a desirable range when dosing 2 part and it just seemed like a waste of time/money. I still test Alk ofc.

I think I’m going to do this as well. Maybe I’ll test every month or so.