Low Alk but High Ca. Recommendations to Right.

[espieg]

Ive had my tank up and running for 3+ years now but only recently started getting into Corals. It’s a 125 g with several small lps and a couple of soft corals. I just tested my parameters for the first time since adding coral a month ago and my Alk is low - 6.1. My Ca is 500ish, mag is 1470, pH is 8.1. I’ve been doing 10 g of water changes a week with reef crystals. What’s the best method for raising Alk subtly and will I need to start dosing?

 

[Kigs15]

I was in a very similar boat using Reef Crystals. For whatever reason I could not get my alk to maintain anything above 6.5ish and no matter how much I dosed sodium bicarbonate my alk would plummet the next day. Calcium was around 550 and mag around 1600 and not lowering. I stopped using RC and moved to regular instant ocean. I did 30% water changes about 3-4 days apart for two weeks. All of a sudden my alk was 9, ca around 420, mag was around 1250-1300, and my alk wasn't plummeting the next day.

Fast forward about two weeks of this stability and all of my corals are nice and happy. The healthiest I've ever seen them with actual NICE growth. I moved to weekly 25% water changes and started dosing AFR and on a 120g system I only need to dose about 15ml a day.

Moral of the story is I would ramp up water changes until you have reach some kind of stability then lower back the water changes and figure out dosing at that point (if you even need it... test, test, test).

 

[Randy Holmes-Farley Verified Community Expert]

Ive had my tank up and running for 3+ years now but only recently started getting into Corals. It’s a 125 g with several small lps and a couple of soft corals. I just tested my parameters for the first time since adding coral a month ago and my Alk is low - 6.1. My Ca is 500ish, mag is 1470, pH is 8.1. I’ve been doing 10 g of water changes a week with reef crystals. What’s the best method for raising Alk subtly and will I need to start dosing?

500 ppm calcium is fine.

For now, just boost alk with baking soda. Here's a calculator. Dissolve a bit in fresh water, and add to a high flow area. I'd boost 0.5 dKH per day until you get to your target. i recommend 7-11 dKH.

https://reef.diesyst.com/chemcalc/chem_calc3.html
Once demand picks up, a balanced alk and calcium method is generally best. There are many types and brands.

 

[Randy Holmes-Farley Verified Community Expert]

Moral of the story is I would ramp up water changes until you have reach some kind of stability then lower back the water changes and figure out dosing at that point (if you even need it... test, test, test).

I'm actually not seeing any reason for a water change for the OP. There's nothing to suggest he has any instability. :)

 

[Kigs15]

I'm actually not seeing any reason for a water change for the OP. There's nothing to suggest he has any instability. :)

You would know better, I'm still a noob.

I only regurgitated what worked for me.

Any insight would be awesome. I was dosing an absurd amount of brs sodium bicarbonate and it would not raise alk more than .5 before instantly falling back to 6.5ish the following day.

 

[rishma]

I don’t worry too much about calcium in that range. My dosing tends to result in Ca creeping up over time. I only test once every few months. Alkalinity I test very often and try to keep in a narrow range. I’d follow Randy’s baking soda recommendation.