New Saltwater Chemistry Changes

[Aaron Atkinson]

Hello. I've been in the hobby for about 6 months and trying to learn about the chemistry of the sport. I recently installed a couple of tanks to store RO/DI and fresh saltwater. The 25 gallon saltwater tank has a small skimmer pump inside which keeps flow and adds air which passes through a CO2 scrubber. (It's in the basement and I've found this helps keep the pH up to the DT level).

What I'm finding is alkalinity is dropping roughly 2-3 dKH over the course of a week. I'm using HW-Marinemix Reefer Salt Mix mixed to 1.026 sg, which comes out at mid 8's alkalinity when fresh. But within the mix tank, I find myself adding soda bicarbonate (baking soda) the day before I do a water change to bring the alkalinity up. I'm wondering if this is normal or not?

Upon inspection of the heater, which is used for about 12 hours before I pull fresh salt water, it pretty much is covered in white/grey solid, which I presume is calcium precipitation. The pump doesn't look like it has much, either on the exterior or roter assembly.

Calcium so starts at 420ish and moves down to 395ish in the span of a week. Magnesium stays steady at about 1360.

Any words of wisdom would be greatly appreciated. Thank you.

 

[Cory]

Everything seems normal to me. A drop of 3dkh per week is a low alk demand

Yeah calcium will precipitate on hot surfaces easier. Thats normal on the heater

 

[Randy Holmes-Farley Verified Community Expert]

IMO, it is not worthwhile to keep the new salt water pH elevated by constantly aerating with lower CO2 air. That is just a waste of media. There is nothing wrong with the pH of new salt water being lower )or higher) than the tank.

 

[Randy Holmes-Farley Verified Community Expert]

I agree it all seems normal. Folks generally lose 0.5 to 4 dKH per day, and with substantial corals or coralline algae, it is usually 2-4 dKH per day.

 

[Aaron Atkinson]

Thank you very much gentlemen. I'll go ahead and switch off the pump, saving on both media and electricity.