Fixing 2 Part Dosing

[moobiecow]

Tank Parameters:
Red Sea Reefer 170 (estimating ~38 gallons)
Alk: 9.1
Ca: 420
Mg: 1400
pH:8.0-8.2

Pair of clowns, mostly LPS, and a RBTA.

Dosing 75 ml/day BRS sodium bicarb (i mix 1 tbsp per 7.1 fl oz in smaller batches) and 10mL/day Red Sea Foundation Calcium +. Never really have to dose any mg since water changes seem to be taking care of it. So far that's been keeping everything stable at these levels.
I've been reading that I should be dosing equal amounts, and noticing some precipitation on the sand bed (hard sand near liverock) and in the sump (i've recently switched to dosing into the tank from the return chamber of the sump). Should I up the dose of Ca of the Red Sea to match the sodium bicarb, or is the dosing okay uneven if the parameters are stable and everything seems to be thriving? Should I switch to BRS calcium chloride and dose the same amount? Should I dose 10ml of sodium bicarbonate and see what happens to alk? (according to the brs calculator this is how much i should be using per day) I’m worried that adding that much Ca will nuke the corals in the tank.

The main reason I use the sodium bicarb from BRS instead of the Red Sea Part B sodium carbonate is because my ph is on the higher side and don't want the spikes associated with the sodium carbonate.

 

[Ron Reefman]

Dosing unequal amounts of Ca and alk is perfectly OK. The goal is to have your Ca and alk in balance in the tank. Your 420 Ca and 9.1dKH alk are just about perfect and almost exactly where I keep my levels.

 

[Randy Holmes-Farley]

Several misconceptions here.

pH 8.0 to 8.2 is not on the high side. it is on the low side.

That said, it is fine to dose sodium bicarbonate for alkalinity.

There is no reason to EVER assume a two part is designed for 1:1 dosing unless it claims to be designed that way (and some that claim it aren't correctly designed). You are using a strange system where you pick one part from one company and the other part from another company. Those definitely are not "designed" by anyone to play together at 1:1.

Specifically, my DIY two part recipe using bicarbonate (that BRS uses) is far more dilute than the calcium part of the Red Sea system (by about 5x), and you SHOULD be dosing much more of the alk part.

Dosing of magnesium when using a two part is not done by testing, but based on the addition of alk and calcium. The changes are too slow to detect with a hobby kit. Many two parts just incorporate it into the calcium part so you never even see it.