Adding KH to RO water making pH too high - The Planted Tank Forum
 10Likes
  • 3 Post By Greggz
  • 1 Post By WaldoDude
  • 2 Post By en7jos
  • 2 Post By pauld738
  • 2 Post By en7jos
 
LinkBack Thread Tools Display Modes
post #1 of 7 (permalink) Old 09-01-2020, 11:53 AM Thread Starter
Algae Grower
 
PTrader: (0/0%)
Join Date: Jul 2019
Location: Canberra, Australia
Posts: 65
Adding KH to RO water making pH too high

Hi all,

I am bit confused with how one goes about remineralising their RO water. I use Salty Shrimp GH+ which gives the water GH obviously. It is when I add KH to the water that Im having issues.

I recently switched from using tap water to getting an RO/DI system, mainly because the pH was a bit high and TDS was too low. I wanted a lower pH to be able to keep more species of shrimp.The pH of my ro water is ~6.2. Now, when I add KH to the water (I've used Bi-Carb Soda and also a 'KH Generator' I got from my LFS) to get a KH of 3-4, I find that the pH of the RO water increases to around 8. Which in mind is a big jump. I thought it was because I was using Bi-Carb soda from my kitchen, as Bi-carb soda has natural alkalinity of ~8. Got a 'KH Generator' from my LFS, who told me it shouldn't increase the pH too much. Just tried it and still, the pH is jumping from ~6.2 to an 8.

So I'm kind of stumped at the moment. I understand that raising KH inevitably raises pH but I don't think its meant to cause this significant of an increase? Otherwise how do people remineralise their RO water and still maintain a reasonable pH? E.g. if Cherry shrimp should be ideally kept at pH ~7 and with a kh of atleast 3 (based on what I could find on google) how does one do that?
I currently only have cherry shrimp and some native aussie shrimp.
WaldoDude is online now  
Sponsored Links
Advertisement
 
post #2 of 7 (permalink) Old 09-01-2020, 02:10 PM
Planted Tank Guru
 
Greggz's Avatar
 
PTrader: (2/100%)
Join Date: May 2008
Location: Novi, MI
Posts: 5,205
How quickly after you add it are you testing?

When adding carbonates to RO water, there is large immediate spike in pH.

Takes quite a few hours for it to stabilize. Sometimes overnight.

That's why it's always better to store water and remineralize rather than dose directly into the tank.
Immortal1, WaldoDude and en7jos like this.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
---
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
---
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Greggz is offline  
post #3 of 7 (permalink) Old 09-01-2020, 02:24 PM Thread Starter
Algae Grower
 
PTrader: (0/0%)
Join Date: Jul 2019
Location: Canberra, Australia
Posts: 65
Oh I see, yes I am testing it once the tds hits what I'm aiming, so pretty quickly after adding it. I'll test it again tomorrow.
Greggz likes this.
WaldoDude is online now  
 
post #4 of 7 (permalink) Old 09-01-2020, 02:25 PM
Planted Member
 
en7jos's Avatar
 
PTrader: (0/0%)
Join Date: Jun 2020
Location: Singapore
Posts: 210
Hi @ WaldoDude,

Hopefully few pointers for you:

- You can't measure the pH of RO water as pH measurements with 0 KH are meaningless. The pH straight out of your RO filter should be about 7, but might drop slightly (becoming slightly acidic) as the water absorbs CO2 from the air. Your pH 6.2 reading is probably not accurate. Think of RO water as a blank sheet with no real pH of it's own until you start adding stuff back into it.

- My shrimp (and many other peoples) do fine at 0KH (because my tanks have Amazonia active soil which eats up all the KH!). I'm guessing you have inert substrate, right? Don't be too concerned about getting to the 3-4 KH mark. Just a sniff of KH in the water (1-2 KH max) should probably be ok for the shrimp and will make it easier to achieve the lower pH that you are looking for.

- How are you measuring your pH? Might be that your results are inaccurate if your pH reading is up at 8 for 3 KH. My planted tanks (with now depleted active soil) sit at around pH 6.8 - 7.0 with 7 GH and 3 KH, so your reading seems a bit on the high side maybe?

Regards, James
pauld738 and WaldoDude like this.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
en7jos is online now  
post #5 of 7 (permalink) Old 09-01-2020, 02:58 PM
Planted Tank Obsessed
 
pauld738's Avatar
 
PTrader: (0/0%)
Join Date: Jan 2019
Location: Modesto
Posts: 333
Yeah, only thing to worry about Kh is to keep it steady.

I'm running 1 dKh on RO water, roughly 6.9 pH in the tank before lights on, a high of ~7.3 ph before lights out and cherries and red rili's are breeding.

I've had tanks in the 4dKh range with the same results. Well higher pH values. :-)

Sent from my Pixel 3 XL using Tapatalk
WaldoDude and en7jos like this.
pauld738 is online now  
post #6 of 7 (permalink) Old 09-02-2020, 12:28 AM Thread Starter
Algae Grower
 
PTrader: (0/0%)
Join Date: Jul 2019
Location: Canberra, Australia
Posts: 65
Quote:
Originally Posted by en7jos View Post
Hi @ WaldoDude,

Hopefully few pointers for you:

- You can't measure the pH of RO water as pH measurements with 0 KH are meaningless. The pH straight out of your RO filter should be about 7, but might drop slightly (becoming slightly acidic) as the water absorbs CO2 from the air. Your pH 6.2 reading is probably not accurate. Think of RO water as a blank sheet with no real pH of it's own until you start adding stuff back into it.

- My shrimp (and many other peoples) do fine at 0KH (because my tanks have Amazonia active soil which eats up all the KH!). I'm guessing you have inert substrate, right? Don't be too concerned about getting to the 3-4 KH mark. Just a sniff of KH in the water (1-2 KH max) should probably be ok for the shrimp and will make it easier to achieve the lower pH that you are looking for.

- How are you measuring your pH? Might be that your results are inaccurate if your pH reading is up at 8 for 3 KH. My planted tanks (with now depleted active soil) sit at around pH 6.8 - 7.0 with 7 GH and 3 KH, so your reading seems a bit on the high side maybe?

Regards, James
Hi @en7jos,

I am using API pH tests (high and low) and I have a pH pen. I understand the issue of measuring pH of ro water but I guess my main concerns largely arose from when I tested the my tanks' water after doing water changes using the ro water. The first couple of weeks before I was adding kh, using the remineralised ro water was causing my tank's ph to steadily drop from 8 (my tap water pH) to around 7.2, which was great and what I wanted. Then I started adding KH and 3-4 days later the pH was back up to ~8. So that's when i started testing the pH of RO water before (but after adding GH+) and after adding kh.

I am actually using an active substrate in both my tanks. 1 of the 2 tanks, has had the substrate (ADA Amazonia) for almost 2 years now so I don't know if still has a buffering capacity, the pH of this tank is the one that's always gone back up to 8. My newer tank has fresh active substrate that I've setup about 3 weeks ago, the pH of this tank fluctuates from around the ~7.8 mark. Which I assume to be because of the active substrate.

So I guess
1. I don't want my new tank to be fluctuating in pH and hence why I want the ro water I'm adding to be of a neutral pH to avoid these fluctuations.
2. I want the pH of my older tank to drop down a bit.

Based on what you said, I will test to see what the pH is at a kH of 1 and see if there's a difference, but yes I do think the jump in pH seems very high hence why i thought I was using the product to raise kh.
WaldoDude is online now  
post #7 of 7 (permalink) Old 09-02-2020, 05:35 AM
Planted Member
 
en7jos's Avatar
 
PTrader: (0/0%)
Join Date: Jun 2020
Location: Singapore
Posts: 210
Hi @WaldoDude

For your new tank, do not add KH and do not use tap water! You are just shortening the life of the substrate! Active soil (e.g. Amazonia) will remove KH from the water and will drop it to zero (or thereabouts). Adding KH is fruitless as the soil will just keep removing it, at least it is depleted and then you have lost all the buffering ability.

If your 3 week old tank has Amazonia substrate, then the pH should be below 6.0 at this stage, settling to around 6.4-6.6 'ish after a few months. If you're adding KH or using tap water then you are raising the pH only for the soil to absorb the KH again and bring the pH back down. Most important thing for shrimp is stability of pH. Chances are you have already used up some of the soil's buffering ability, so my advice would be to stop adding KH, use RO water with just GH+ added, and just let the tank settle and stabilise. See where the pH settles; if you're lucky the pH will come down to low to mid 6's. If the buffering capacity of the soil has been partly depleted, then maybe mid to high 6's to low 7's (but I wouldn't have thought you could have depleted it that much in only 3 weeks).

For your older tank, at 2 years old and having used tap water / added KH, think you can assume that the buffering capacity has been completed depleted. Again, just use GH+ in your RO water (don't add any KH) and see where the pH settles over the course of a couple of weeks after a series of smaller water changes. This tank probably won't get down to 0KH if the soil is exhausted.

Don't try to fight the active substrate! Let the KH be zero and see where the pH settles. Stability is the most important thing. Shrimp do not generally need KH with an active substrate.

A pH of 8 still seems a bit high to me for a KH or 3-4.....?

I've set up 5 shrimp tanks over the course of the last 6 months with Amazonia substrate and have done a lot of learning about soil / KH / pH / shrimp in that time, and have made lots of mistakes! For reference here are where my tanks sit now in terms of KH and pH, just to give you something to compare your tanks too and give some range to pH values to be expected:

*Planted fish tank, 6 months old, started using 4GH and 2KH tap water plus added crushed coral to filter to try and keep KH up (doh!). Buffering capacity of soil now fully depleted, KH sits at 3-4 despite not having added KH for months (assume somehow leaching back out of soil or maybe the rocks). pH sits at 6..8 to 7.2. This sounds very much like your 2 year old tank?

*Shrimp tank with moss, 4 months old, RO water and GH+ from start, added little KH+ at start when cycling to try and keep pH up as struggled to get it to cycle at low (<6.0) pH. Now sits stably at pH 6.6, 6GH and 0KH. Think this is fairly representative of a mature Amazonia soil tank in which buffering capacity has not been depleted.

*2 month old shrimp tank, RO water with GH+ only from start, never any KH added, was just patient this time and let the cycle slowly (1.5 months) happen at the low pH. Now stable at 6GH and 0KH with a pH of 6.0 or maybe less (my API test kit only goes down to 6.0, but I'm guessing actual pH is about 5.6-5.8 from what I've read about the soil). This should be fairly representative of a new Amazonia soil tank where the substrate has not been depleted at all.

Hope that gives you some context?

Regards, James
Quesenek and WaldoDude like this.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
en7jos is online now  
Reply

Tags
high ph, increasing kh, remineralising, ro/di water

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the The Planted Tank Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome