KH - What’s the Magic # and WHY!?

[krash7172]

"explain how you decided on your KH"

My mostly softy mixed reef is stable around 8.5-9.0 with monthly WCs and occasional ALK dose. I only check ALK if I don't do a regular WC. Critters are happy

 

[Sdot]

Howdy Reefers,

What is the magic number for KH and why?

Please list your current KH and these other major parameters and explain how you decided on your KH.

KH - ?
Salinity - ?
CAL - ?
MAG - ?
Phosphate - ?
Nitrate ?

Here is mine:
KH - 10.0
Salinity - 1.025
CAL - 475
Mag - 1450
Phosphate - .05 - .08
Nitrate - 10 ppm

I run my KH @ 10.0 because it increases my PH especially in winter months in Cleveland, OH when I can’t count on fresh air to raise the PH of the tank. I tend to run everything a bit higher due to this.

KH - 7.2 - 7.5
Salinity - 1.026
CAL - 420
MAG - 1320
Phosphate - (.05 -.1)
Nitrate - (8-15 ppm)

My Tank

 

[kenchilada]

8-9dKH for acros always was my sweet spot for good growth/colors, easy to control nutrients without burned tips.

 

[Tastee]

I run my tanks on AquaForest Reef salt and Component 1+2+3+ dosing and target close to Reef salt standard parameters.

kH 8.1-8.4
Ca 380-420
Mg 1400-1600
pH 8-8.2

My Nitrates and Phosphates are quite low (NO3 0.1-.5, PO4 ~.1 at most), just due to Coral uptake as I don’t run GFO, NoPoX etc. In my larger tank I’m feeding both fish and corals more to bring them up as some of the LPS were struggling. Levels are still low but the corals are much happier, so that’s good enough for me. In the smaller tank the corals are doing fine so I’m just continuing to feed the fish a bit heavy but not feeding the corals anything specific. For the corals I use Reef Roids and have recently started feeding Red Sea Coral Nutrition AB+ - good results so far.

 

[Reefinmike]

Randy raised some important points here https://www.reef2reef.com/threads/alkalinity-stability-ph-stability-are-they-even-different.711768/ . I've spent the last 6 months doing experiments and feel pretty confident saying that "alkalinity" number really carries little weight. I managed to get one reef down to 4.8DKH and sps coral were happy as can be...

In the wild, carbonate and bicarbonate ions stem from atmospheric CO2. CO2+H2O= H2CO3(carbonic acid). from there it can disassociate into a bicarbonate(HCO3) or carbonate(CO3) Ion but this is all dependant on the concentration of free hydrogen ions in the solution(pH). CO2 isn't a bad thing... it's actually coral's carbon source just like terrestrial plants. That said... I feel alkalinity levels/control should be more focused on the extremes of the spectrum... CO2 and OH(hydroxide) dosing.

 

[EakTheFreak]

The part I find the craziest is the variance in different types of salts. I see many people are at 8.0 kh and when I was viewing different salt blends it appears that many of the premium salt blends are at 10-12 kh.

That would throw your ALK off everytime you did a water change wouldn’t it? I suppose if you are doing 10% weekly it wouldn’t be an issue.

I personally do 25% every other week with Fritz RPM Red box with High AlK that ranges from 10-12 dkh.

 

[EakTheFreak]

Looking like 8.5 may round out as the winner!

Let’s see some more votes!!!

 

[chadfish]

I (try) to keep my KH @ around 8.5 based on Randy Holmes-Farley's article here:

Optimal Parameters for a Coral Reef Aquarium: By Randy Holmes-Farley

[note: last updated edited on 8/10/2022] One of the main roles of an aquarist with a coral reef aquarium is to ensure that the conditions are right for their tank inhabitants. There are many different attributes of the aquarium that need to be...

www.reef2reef.com

In summary, the goal is to keep alkalinity high enough to help corals build mass, while not being so high as to accelerate precipitation on pump impellers and other equipment.

Here's how my alkalinity varies throughout a few days, compared against when I dose liquid soda ash (green line disappeared today once I figured out how to setup up "controlled dosing" with my Trident!)

Other key water parameters:

pH - 8.1 to 8.3
Salinity - 1.025
Calcium - 400ppm
Magnesium - 1300ppm
Phosphate - 0.03ppm
Nitrate - 2ppm

How do you get continuous digital kh readings like this?

 

[EakTheFreak]

I auto dose Alk and Cal due to the high consumption in my heavily stocked mixed reef. Manually dose Mag.

PH - 8.1 to 8.3
KH - 8.5 to 9.0
Salinity - 1.026
CAL - 420 to 440
MAG - 1400 A little high for me. letting it fall slowly to hopefully 1350ish.
Phosphate - .08
Nitrate 16ish

I've been getting some GHA for a while now. May adjust my NO3 and PO4, but I'll do it slowly and hopefully without using chemicals or GFO.

How much do you dose in ML for ALK & CALC

 

[trmiv]

I shoot for 8.5. I couldn’t decide between 8 and 9. 8.5 was in the middle so I went for it.

My alk is maintained through Trident controlled dosing so it doesn’t tend to vary more than .1 dkh through the day.

 

[Auquanut]

How much do you dose in ML for ALK & CALC

200 ml each of BRS calcium chloride and soda ash solutions. Auto dosed over 12 doses each daily on alternating hours in a 125 gallon tank.

 

[XRayLee]

This is probably a dumb question, I'm fairly new to salt water reefing. I have my salinity at 1.023 which looks to be a little low compared to other reefers readings on here. I only have a couple pieces of live rock with 3 soft coral right now which all seem to be doing quite well. Should I bump up the salt to 1.025-26? The tank has been up since November 2020.

 

[Garf]

This is probably a dumb question, I'm fairly new to salt water reefing. I have my salinity at 1.023 which looks to be a little low compared to other reefers readings on here. I only have a couple pieces of live rock with 3 soft coral right now which all seem to be doing quite well. Should I bump up the salt to 1.025-26? The tank has been up since November 2020.

Yes, I would. If you ever post a problem on here, rightly or wrongly your salinity may be blamed. Best to take that out of the equation and get it to .025/6 using a calibrated method.

 

[cryptodendrum]

Background:
I run a mostly automated / strictly controlled Hybrid setup of both Kalkwasser & Baling Lite for maintaining levels and auto-top up. I do this because Kalkwasser isn't able to do the job on it's own due to my water volume of my system, so I use Baling salts to close the gap in maintaining CA and KH when necessary.

Kalkwasser is added via a constant flow Kalkwasser Reactor Bucket which is not a sealed system; but it is based off a description I read Randy Holmes-Farley had described, in which he described he didn't think it needed to be sealed. I'm able to dump in 500grams of Calcium Hydroxide as a recharge about every 90 days to keep pH in the reactor at or above 12. Kalkwasser is dosed at a pre-set daily rate split across 12 hours, every hour, via a controller-based auto-doser during the night / lights out cycle which does a good job of minimising daily day/night pH swings.

And this approach helps save some money over time on the cost of Baling Salts for CA / ALK. Which adds up as my system is approx 2500 litre system of 7 interconnected tanks currently (3 Display tanks + 4 working tanks). It's mostly a mixed tank of SPS, LPS and Softies. I've used this approach since 2007 with really excellent results and only a few precipitation accidents in the first year or two as I learned better how to operate such a setup; there's not been a precipitation event since then nor on my heaters or pumps.

And I run all the water values (pH / CA / ALK / MAG ) a bit on the "hot" side, including a daily peak of pH at 8.64.


I *try* to run it at 8.5, but since the Jan 2020, when I added two my two first Monti frags - each the size of just a little larger than my thumbnails... and each which have now grown much larger (see photo), holding CA, Mag and Alk levels stable has been a little more "challenging". My Baling Lite Alk daily additions had to be upped from 86ml a day to over 200ml now, which I'll have to increase soon again, as even that's not enough to maintain a steady dkH - as those Monti's are growing and their frags put else where in the tanks take off on their own. As evidence between the two photos - I've had to put Monti frags from the Reef tank (above photo taken in Nov 2020)into the Anemone tank (below photo taken just this week in March 2021). And my LPS all grow at pretty excellent rates as well. I currently am overdue for a harvest of my LPS, which results in me taking out between 30% to 50% of the LPS you see here & which goes back into retail supply via a local LFS.

 

[Strangewaterchange]

I was running it around 7 using TMPro when I started my first reef tank about a year ago but then Ryan from BRS said I could achieve 70% more coral growth by upping it to 9 so I gradually switched to hw-marinemix at 9 dkh and all I can say is he was absolutely right.

 

[368]

NSA is btw 7-8kh. If you keep coral in your tank and don’t have an auto doser in 2021, what are you doing?

 

[Ferrell]

One tank is happy at about 8.2-8.3, other is happy at 8.4-8.5. Nutrients vary in each, one runs low 5 no3 < .1 PO4, other likes a little higher. Just all according to what the tank wants.
I use HW Reef salt and Ca hangs between 340-360 and Mg around 1500 (mg always higher in this salt) Only difference between tanks is two part for one and kalk for the other.

 

[AquaBiomics]

I've never seen a coral that was happier at dkh > 7 than at dkh = 7. Small wonder since that is the level in the ocean.

I suspect that trying to maintain unnatural alkalinity is one of the biggest contributors to problems growing corals.

 

[X-37B]

I've never seen a coral that was happier at dkh > 7 than at dkh = 7. Small wonder since that is the level in the ocean.

I suspect that trying to maintain unnatural alkalinity is one of the biggest contributors to problems growing corals.

Well put!
I run a carx.
Alk 7.2
Ca 420
Mag 1350
Sg 1.026
Temp 79-81
Po4 .06-.1
No3 5-10.
For the big 3 close to NSW is my goal.
If its good enough for the ocean its good enough for me.
I get very good growth at that level.
Stabilty wins, whatever your level is.

A big pet peave of mine is quite a few well known and not so well known people will tell you the oceans alk is 8-9. Look it up as im not going to name names.
Not sure what planet they are living on, lol.

 

[XRayLee]

Yes, I would. If you ever post a problem on here, rightly or wrongly your salinity may be blamed. Best to take that out of the equation and get it to .025/6 using a calibrated method.

Thanks, and will do that with a water change today.