Ratios

Aaron88 · Jul 11, 2020

So I have heard that current ratios is important in reef tanks, in respects to Ca Mg DkH. But I have had a hard time finding any such ratios. So let’s say my Ca is at 460 what should be DkH and Mg be at? What is the math behind it?

Randy Holmes-Farley · Jul 11, 2020

Aaron88 said:
So I have heard that current ratios is important in reef tanks, in respects to Ca Mg DkH. But I have had a hard time finding any such ratios. So let’s say my Ca is at 460 what should be DkH and Mg be at? What is the math behind it?

IMO, very few ratios are suitable for reefkeeping targets.

In the case of calcium, magnesium, and alkalinity, they certainly are not the way to go.

Each parameter should be independently targeted to an optimal value. Having all of them low or high (at a fixed "optimal" ratio) is certainly not desirable.

i would target 7-11 dKH, and if nutrients are very low, i'd target alk in the 7-8 dKH range.

Magnesium in the 1250-1400 ppm range is good.

Calcium in the 400-550 ppm range is good.

Aaron88 · Jul 11, 2020

Right now I’m at;
Kh 7.3
Ca 460
Mg 1400
pH 7.8

I’m trying to bring up my Kh to hopefully get my pH up. But over the last 8 months it’s been just as you read.

Dkeller_nc · Jul 11, 2020

It's quite easy to bring your calcium levels down to be more in line with your alkalinity - simply stop dosing calcium for a few days. OTOH, bringing your alkalinity up may potentially be very easy (just dose more over several days), or possibly quite difficult, depending on the age of your tank and the number of inhabitants. If the tank is very new (<6 months) or sparsely inhabited, you may find that increasing the alk above 8 may be quite difficult because they just aren't enough dissolved organics in the water. That's despite the normal to high magnesium concentration, which also plays a role in keeping carbonate and calcium in the water from precipitating.

Temperature also plays a role in this (as do several other parameters, like pH). The abiotic precipitation of calcium carbonate is very sensitive to temperature - higher temperatures increase the rate of precipitation.

Randy Holmes-Farley · Jul 11, 2020

Aaron88 said:
Right now I’m at;
Kh 7.3
Ca 460
Mg 1400
pH 7.8

I’m trying to bring up my Kh to hopefully get my pH up. But over the last 8 months it’s been just as you read.

Those values are fine. pH is best solved by going after CO2, not raising alkalinity.

Aaron88 · Jul 11, 2020

Randy Holmes-Farley said:
Those values are fine. pH is best solved by going after CO2, not raising alkalinity.

Going after CO2? That doesn’t sound easy.

Randy Holmes-Farley · Jul 11, 2020

Aaron88 said:
Going after CO2? That doesn’t sound easy.

It is. Open windows is the easiest way.

This has more:

pH And The Reef Aquarium
http://www.reefedition.com/ph-and-the-reef-aquarium/

andrewey · Jul 11, 2020

Not as complicated as you would think. There are many ways to skin this cat- use of a skimmer, powerhead pointed at the surface to break the surface of the water, route skimmer airline outdoors, use CO2 scrubber, reverse photo period of refugium, etc.

Easiest way of all: open some windows