KH is Stuck

My KH has been stuck at 15 for months now and I am not sure how to get it down. I was trying to be patient and let it fall naturally but it doesnt seem to be happening. I do routine water changes and it still stays there. Here are my other numbers:

Ph - 8.4
Temp - 79.5
Amm/Nitrite/Nitrate - 0
Salniity - 1.024
Ca - 440
Mg - 1200
Phosphate - 0.5
KH - 15

How do I get the KH down safely. Also could a high KH prevent coral growth?

 

I wonder if your test kit reagents are bad. Have you taken a sample of water to your LFS to doublecheck your results?

 

No...I havent taken my water to any LFS.
It's sorta brand new API KH test...maybe a 2-3 months old.

 

It does change to the right colors ....Blue to Green then Yellow....it just takes 15 drops to get a yellow color

 

raw ro/di water should have a 0 dkh. also test your salt water newly mixed water prior to WC. sometimes your salt brand has a higher dkh. Ive ran at 13-15 dkh for last 6 months. running your calcium at 400 might help as higher calcium levels are proportional to higher dkh levels. I've also read seltzer water lowers your dkh. maybe add that to your buckets of WC water after mixing salt and test it to see if it works before dumping into tank. I've had a little success at running my salty tank at 1.026 and doing a 10% WC with just plain ro/di water to get my dkh down a notch. this does lower your tank salinity a little maybe to 1.024 depending on your tank size.

Balanced Calcium and Alkalinity Ratios
1.4 dKH to 350 ppm
2.1 dKH to 375 ppm
5.6 dKH to 400 ppm
9.1 dKH to 425 ppm
12.6 dKH to 450 ppm
16.1 dKH to 475 ppm

 

Adding seltzer/soda water will lower your ph because of the CO2, so be careful with this.

1. What Salt do you use? Seachem salt has a higher borate concentration, which can falsify results of most test kits, causing the reading to show higher than it really is.

2. What are you using to dose your alkalinity?

3. Do you have corals/ etc. that consume alk and calcium? Is your tank fairly new? Do you have much coralline growth?

4. I wouldn't do anything but water changes to bring alk down... 15 dKh is not a dangerous level, just make sure that you do not add more dkh or calcium to too high of a concentration, or it will precipitate.

Here's a good comprehensive read on Alkalinity: Chemistry and the Aquarium - Randy Holmes-Farley

 

Ok..I'll let the calcium drop a little to see if that comes down with it. I will also test my next batch of water to see what the levels are with it.

I use Instant Ocean salt right now, not sure if thats one of the ones that has higher KH levels.

Maybe I'll add some seltzer to the next water change also. I wonder if they like mandarin orange or lemon flavored?!?!

 

The age old adage; "If it isn't broke, don't fix it", applies here. Many run Alk at 15 DKH, myself included, at times. Is there something "wrong" in your tank? Why do you think it needs to be lowered? I would leave it alone and as the buffering capacity of the tank regulates itself, it will fall accordingly.

 

+1 that was my thought exactly

 

You could be on to something....

There is nothing wrong in my tank at all. Things look good, I just didnt know if a higher KH would hinder coral growth.

And I have read many times the range for our tanks should be 8-12 so I thought I should have mine in there.