PH keeps going high....should I worry?

My tap water is well water through a softener. Out of the tap I get:
pH 7.5
GH. 0
Kh. 21

For the aquarium I mix tap water with water from the bypass to give a GH of around 6. This doesnt alter the kh which is around 20 in the aquarium.

In my 37g aquarium, I have the usual small gravel substrate, three lumps of orange lavarock all bought from the local fish store, driftwood and live plants. The aquarium has been running for many years and is fully cycled. I do a 40% water change weekly.

After the water change, the pH is roughly the same as the tap water, ie 7.5 to 7.6. However within 48 hours it increases to 8.0 and sits there until the next water change. This is tested using the API master high range test.

I have done the "let the tap water stand for 24h" test and the pH didn't change.

I cannot work why the pH should increase like this. I am told that stable pH is important, and I am worried that weekly swings from 7.5 to 8.0 is not stable.

Any ideas why the pH should increase like this and should I worry?

 

You have more water surface agitation in your aquarium vs a glass of water sitting. The aquarium will tend to reach equilibrium with the gas in the atmosphere which means you will have low C02 levels (like 2-3 ppm). With low C02 and very high KH from your softener, you get a pH of 8.0.

This is not a problem if you have a good bio filter.

The only problem with high pH (8.0 + ph) tanks is that ammonia is much more toxic at high pH. But if your cycle is well established I would not mess with success!

pH swings are natural and fish are adapted to them. The problem is when the pH goes out of range and cause toxicity of ammonia at high pH.

I would not worry. Just keep an eye on ammonia and realize that for you, ammonia is much more toxic than a 7.0 pH tank.

Here is the chart: http://www.blueridgekoi.com/wp-content/uploads/2014/03/pH-and-Ammonia.pdf

 

There is a relationship between pH, KH and dissolved CO2.

CO2/pH/KH table

An alkalinity (KH) of 20 is unusually high The accompanying pH of 7.5 is an indication that there is a lot of dissolved CO2 in the tank. The CO2 forms carbonic acid when dissolved in water. That neutralizes the alkalinity, allowing the pH to decrease.

As the CO2 gets used by your live plants and stripped from the water due to agitation at the water surface, there is no longer sufficient CO2 to neutralize the alkalinity and the pH rises.

There are a number of options:

1. Do nothing differently. If the tank has been running for years and the plants and animals are doing well, it might be best to just leave well enough alone.

2. If you pour your water changed water into a container and use an air stone to cause water circulation and gas exchange at the surface of that container, the pH is likely to rise over a 2 day period just like it does in your tank. The disadvantage of doing this is that your plants will no longer have access to the CO2.

3. You can add a CO2 injection system so that the level of CO2 remains high, neutralizing the alkalinity and keeping the pH lower than equilibrium.

4. You could add an acid such as sodium bisulfite to neutralize the high alkalinity, but adding chemicals like this is generally not a good idea, so while I mention this as an option, I am not recommending it.

 

Many thanks for these replies which are very useful.
I think for now the answer is to do nothing and keep on as I am.
My fish seem happy enough so it looks as if the weekly pH swings from 7.5 to 8.0 are nothing to worry about
Thanks again

 

I am assuming you are talking about 6 dGH and 20 dKH, not 6GH and 20KH.

your pH goes to 8.0 because of the high KH buffering the acids produced, 1, from the CO2 absorption from the atmosphere as it equalizes, and 2, from the nitrification process. highest it can go is about 8.2 max like that. before it's too alkaline and acids just don't cause much use of the carbonates.

With a KH of 20dKH it's very alkaline.
in fact, the 8.0 pH comes to around 22.4 dKH. or about 400 ppm KH. (Carbonates)

Yes, pH 7.5 is about 21 dKH.

Can you advise what is your well water parameters are on the bypass of the softener?

As I understand it a water softener replaces both Magnesium and Calcium ions with Sodium ions and captures the Mg and Ca ions while doing that. it doesn't do anything to KH. That being said to clean out the Mg and Ca, Sodium chloride is used on a flush out cycle. to unbind the Mg and Ca ions it's captured from the water so it can capture more.

I've heard of old systems using and of people using Sodium Bicarbonate (baking soda) or Sodium Carbonate (washing soda) in place of Sodium Chloride. I'm curious if the bypass water is the same KH, as the softened water or lesser, and if you can sample without the softener in the line at all, maybe from an irrigation system pump on the well before the softener......
potassium Chloride would be a better softening method than sodium chloride as far as plants are concerned.

Wondering what the parameters are without a softener on it at all. Likely both are high, but curious to find out.

 

I am assuming you are talking about 6 dGH and 20 dKH, not 6GH and 20KH.

your pH goes to 8.0 because of the high KH buffering the acids produced, 1, from the CO2 absorption from the atmosphere as it equalizes, and 2, from the nitrification process. highest it can go is about 8.2 max like that. before it's too alkaline and acids just don't cause much use of the carbonates.

With a KH of 20dKH it's very alkaline.
in fact, the 8.0 pH comes to around 22.4 dKH. or about 400 ppm KH. (Carbonates)

Yes, pH 7.5 is about 21 dKH.

Can you advise what is your well water parameters are on the bypass of the softener?

As I understand it a water softener replaces both Magnesium and Calcium ions with Sodium ions and captures the Mg and Ca ions while doing that. it doesn't do anything to KH. That being said to clean out the Mg and Ca, Sodium chloride is used on a flush out cycle. to unbind the Mg and Ca ions it's captured from the water so it can capture more.

I've heard of old systems using and of people using Sodium Bicarbonate (baking soda) or Sodium Carbonate (washing soda) in place of Sodium Chloride. I'm curious if the bypass water is the same KH, as the softened water or lesser, and if you can sample without the softener in the line at all, maybe from an irrigation system pump on the well before the softener......
potassium Chloride would be a better softening method than sodium chloride as far as plants are concerned.

Wondering what the parameters are without a softener on it at all. Likely both are high, but curious to find out.

Hi there thanks for the reply.
The water softener is a modern one, installed last year and uses salt tablets.
Through the softener I get a GH of 0...by which I mean 1 drop from the API test kit goes green.
I have an outside tap that bypasses the softener so is pure well water. This has a GH of around 25...is it takes 25 drops to go green.
As you surmise, the kh is the same from both sources.
What I do is to mix 25% bypass water with the softened water to give me around 6 gh.ie 6 drops to turn green.
Thanks again

 

Another option would be distilled or RO water, and mixing 3 RO or distilled to 1 part before the filter water and this should get you in the neighborhood of 6 dGH and 5 dKH. I don't know if RO is an option, but cutting the extreme highs by that much with 0 water should get it all in line. maybe 6 parts RO to 4 parts before the softener water and getting 10 dGH and 8 dKH. the thing is your softened water is running high KH and it is before softening, so there's no change to it also by cutting it. 20 dKH and 20dKH = 20dKH.
but 20dKH and 0dKH, at a 50/50 will cut it in half to 10dkH and the right mixture will lower it to where you want it to be.

For a free source you could cistern and collect rain water, just collect some and test it and see if it's running really low or 0s also before using it.

Ideally theres a lot of carbonates and sodium the plants just aren't gonna like in the softened water. and bringing it down would be better than leaving it but it might involve needing to premix and let the water age for 48 hours to stablize before using it.

it's true, you might not have any issues with pH or much problems with plants or the fish with KH that high, but it might cause stress issues on the fish and they get sick more often, or inhibit breeding or viability of eggs and fry for species that don't really like the higher pH and hardness of the KH.

if you keep african cichlids, I think you are about good to go for lake malawi though tright where you are!

if you want to discuss any of this more, it can be. you wouldn't want to slam the fish into 6GH and 8KH and 7.0 pH or 6.6 from the highs you have, there's ways to water change and bring it down over time, even just waterchanging with cistern collected rainwater and slowly bringing the tank down over time through the water changes with zero water. and then doing the mixing to keep it where you want it. once it's in line where you want it.

 

Another option would be distilled or RO water, and mixing 3 RO or distilled to 1 part before the filter water and this should get you in the neighborhood of 6 dGH and 5 dKH. I don't know if RO is an option, but cutting the extreme highs by that much with 0 water should get it all in line. maybe 6 parts RO to 4 parts before the softener water and getting 10 dGH and 8 dKH. the thing is your softened water is running high KH and it is before softening, so there's no change to it also by cutting it. 20 dKH and 20dKH = 20dKH.
but 20dKH and 0dKH, at a 50/50 will cut it in half to 10dkH and the right mixture will lower it to where you want it to be.

For a free source you could cistern and collect rain water, just collect some and test it and see if it's running really low or 0s also before using it.

Ideally theres a lot of carbonates and sodium the plants just aren't gonna like in the softened water. and bringing it down would be better than leaving it but it might involve needing to premix and let the water age for 48 hours to stablize before using it.

it's true, you might not have any issues with pH or much problems with plants or the fish with KH that high, but it might cause stress issues on the fish and they get sick more often, or inhibit breeding or viability of eggs and fry for species that don't really like the higher pH and hardness of the KH.

if you keep african cichlids, I think you are about good to go for lake malawi though tright where you are!

if you want to discuss any of this more, it can be. you wouldn't want to slam the fish into 6GH and 8KH and 7.0 pH or 6.6 from the highs you have, there's ways to water change and bring it down over time, even just waterchanging with cistern collected rainwater and slowly bringing the tank down over time through the water changes with zero water. and then doing the mixing to keep it where you want it. once it's in line where you want it.

Thank you, that's all good to know. I do have a RO filter, but it's throughput is quite slow, we just use it for drinking water.
I'll have a think, I'm not going to change anything too quickly.

 

The only cost effective way to treat high KH water is to remove the carbonates. To do that you have to treat the water as described here if you have the safety skills.

Using the hydrochloric acid to lower alkalinty | Advanced Freshwater Aquarium Topics Forum | 483564