How to raise KH in very hard water

[Katya]

My tap water is very hard (GH) but has little buffer (KH) (around 40 PPM) and the pH tends to the low side (around 6.7-6.8).  Is there a good way to raise the buffer to prevent pH swings?  I tried Seachem Neutral Regulator, but a couple of times after adding it, I observed white stuff apparently precipitating out of the water.  I have a small tank, and I can only find 20- or 40-pound bags of crushed coral at the local store (is crushed coral even the best option?  Would a Wonder Shell work?).  Or is it okay that the pH is a little on the acidic side?  (I have some live plants, a betta, and a snail, in case that matters.)  Thanks!

[colo3000]

I have pretty high GH and low KH naturally and have used crushed coral in a mesh bag in my HOB filter which worked well for raising the KH. I also only have one tank so I just have a large bag of crushed coral in my closet which doesn't bother me. I would personally advise using crushed coral if you don't mind storing the rest somewhere. I think Aquarium Coop also sells small 1lb bags of crushed coral but you would obviously be paying a lot more per pound, but maybe the quantity is more of a burden than a benefit to you. Good luck!

Edited November 16, 2021 by colo3000

[Mmiller2001]

The problem with crushed coral or wonder shell is that they both raise GH and KH. If you want to raise just KH, look to potassium carbonate or potassium bicarbonate or even baking soda. Baking soda will add salt to the tank and the potassium options add potassium.

I choose the potassium options as I keep planted tanks.

[GardenStateGoldfish]

I have very similar water to you, i would just grab a small bag of crushed coral and keep it on hand if you ever need it, I have a 55 pound bag I have about 15 pounds left off just overtime (long time) of using crushed coral in filters. I have 300ppm plus of GH but about 40 KH and the crushed coral has been create as a KH buffer making it way longer before my ph starts to drop, my ph is about 6.8 from the tap also. 

[Tanked]

On 11/16/2021 at 4:54 PM, Mmiller2001 said:

The problem with crushed coral or wonder shell is that they both raise GH and KH. If you want to raise just KH, look to potassium carbonate or potassium bicarbonate or even baking soda. Baking soda will add salt to the tank and the potassium options add potassium.

I choose the potassium options as I keep planted tanks.

I've been looking to raise only the KH for a while now.  At 300+ my GH is already too high.  Do you use Carbonate or Bicarbonate, and at what dosage?

[Mmiller2001]

On 11/18/2021 at 8:03 AM, Tanked said:

I've been looking to raise only the KH for a while now.  At 300+ my GH is already too high.  Do you use Carbonate or Bicarbonate, and at what dosage?

I use potassium carbonate as it's cheap and readily available on Amazon. I use the food grade options.

CellarScience - AD640LB Potassium Carbonate (lb) https://www.amazon.com/dp/B074D9BXRT/ref=cm_sw_r_apan_glt_fabc_FY319H70WYG7XACTQHCF?_encoding=UTF8&psc=1

I use https://rotalabutterfly.com/nutrient-calculator.php to make the calculation.

Example, I want to set my 75 gallon tank to 3dKH. I've calculated my 75 gallon to have around 66 gallons of actual water. So I plug it in like this.

So 18.46 grams will give me 3dKH. Try not to alter water with live stock more than 1.5 degree in 24 hours.

It's important to understand that the potassium needs to be accounted for when fertilizing. 

Before I moved my tanks to 0dKH, I used almost no potassium as the K2CO3 added all I needed.

Edited November 18, 2021 by Mmiller2001