Water Source Change, How to Manage Transition

[Clawhammer]

Hi water experts, I have a pressing question:

My water company switched to groundwater about a month ago due to finding a parasite in our typical water source (bull run reservoir). The water properties are quite different, with Bull Run being much softer and lower in pH.

Bull Run - 6.8 pH, <1 dKH, 2-3 dGH
Ground Water - 8.2 pH, 6 dKH, 7 dGH

When the change to groundwater happened, it stressed my discus for a couple days as I did 50% daily changes. My concern now is, how to change back to Bull Run considering this time I will be going to a much lower pH, which I understand to be much more stressful for the fish.

[Clawhammer]

bump...

[Clawhammer]

Maybe just a series of small water changes throughout the day?

[Clawhammer]

I went ahead and did a 50% wc. I added a little baking soda in the middle of the refill to ease the stress and bump up the KH. The fish acted just fine throughout.

[Jack L]

just saw this, but you did what i would have done.
small changes to ease the transition

[Filip]

Sorry for a delayed response here Eric .
I wonder how did the transition end up ?
To tell you honestly with a PH diffrrence with a downward swing of 1.4 degree I would have gone with a lot less water changes than your initial 50% , but it seems that your discus ,on my amazement , have accepted the pH drop of 0.7 degrees just fine .

[Clawhammer]

Sorry for a delayed response here Eric .
I wonder how did the transition end up ?
To tell you honestly with a PH diffrrence with a downward swing of 1.4 degree I would have gone with a lot less water changes than your initial 50% , but it seems that your discus ,on my amazement , have accepted the pH drop of 0.7 degrees just fine .

Hi Filip.

Yes, they were absolutely fine, swimming in the new water during the change. I did add two 1/2 tbsp doses of baking soda as I refilled the tank, which is my standard practice to add some KH to my tank. I think this helped.

[alron2]

Eric,
One tbsp in how many gallons added. That is a significant fact you left out. So what was the tank ph before and after the 50% water change?
Ron

[Clawhammer]

Eric,
One tbsp in how many gallons added. That is a significant fact you left out. So what was the tank ph before and after the 50% water change?
Ron

I didn't leave it out (post 4). My tank is a 120, and I did a 50% WC, so 60 gallons. pH in the tank right now is 7.0

I have found that my normal water (Bull Run) much more stable if I add baking soda as my kh out of the tap is non existant (< 1 dKH)

[nc0gnet0]

People often make incorrect assumptions in regards to pH.

Many would think the following:

50% water at a pH of 6.0 + 50% water at a pH of 8.0 would equal a mixed value of a pH at 7.0.

However, this is not the case at all. Quite often mixing the two will result in a pH much higher than this, if there is a change at all.

I am actually quite surprised in this case it worked out that way, are you sure?

[Clawhammer]

People often make incorrect assumptions in regards to pH.

Many would think the following:

50% water at a pH of 6.0 + 50% water at a pH of 8.0 would equal a mixed value of a pH at 7.0.

However, this is not the case at all. Quite often mixing the two will result in a pH much higher than this, if there is a change at all.

I am actually quite surprised in this case it worked out that way, are you sure?

Quite right, since pH is logarithmic, the pH dropped slowly, especially adding the baking soda. 7.0 is where I have stabilized (its been a week since the OP), and where I typically ended up after adding 1 tbsp of baking soda per 60 gallons before the temporary water source change. This is why the fish tolerated it so well, the pH did not drop dramatically despite regular size water changes.

[alron2]

I didn't leave it out (post 4). My tank is a 120, and I did a 50% WC, so 60 gallons. pH in the tank right now is 7.0

I have found that my normal water (Bull Run) much more stable if I add baking soda as my kh out of the tap is non existant (< 1 dKH)

Sorry Eric I missed it.
Ron

[Filip]

People often make incorrect assumptions in regards to pH.

Many would think the following:

50% water at a pH of 6.0 + 50% water at a pH of 8.0 would equal a mixed value of a pH at 7.0.

However, this is not the case at all. Quite often mixing the two will result in a pH much higher than this, if there is a change at all.

I am actually quite surprised in this case it worked out that way, are you sure?

This is an eye opener for me Rick :).
I guess KH values play an important role on the final PH value when 2 different level PH water sources are mixed and it doesn't comes down to just doing a simple Math.

[DJW]

When you mix water having a strong acid and a strong base, and there are no buffers involved, adding half pH 6 and half pH 8 would result in pH of 7. The H and the OH would combine to form water.

But natural water is different, it is buffered by carbonates and (mostly) bicarbonates. As you add the acidic water to the higher pH water, the carbonate alkalinity (KH) within the more alkaline water consumes the acid so that the pH will only go down slightly.

[RogueDiscus]

When you mix water having a strong acid and a strong base, and there are no buffers involved, adding half pH 6 and half pH 8 would result in pH of 7. The H and the OH would combine to form water.

But natural water is different, it is buffered by carbonates and (mostly) bicarbonates. As you add the acidic water to the higher pH water, the carbonate alkalinity (KH) within the more alkaline water consumes the acid so that the pH will only go down slightly.

I'll actually get a white precipitate on the bottom of my tank if I go more than a couple days without a WC. I've always assumed it was the neutralized carbonates falling out of solution.

[DJW]

Some of that might be caused by evaporation. Calcium carbonate is barely soluble in water, and when it does dissolve it does so very slowly in the ground over a long period of time, so that when hard water comes out of the ground it can be at or near saturation.

CaCO3 is unusual. Most solids get more soluble as the temperature of the water increases, but CaCO3 does the opposite. We take cold well water and warm it up, which brings the CaCO3 closer to, or beyond, saturation, and then over time as the water evaporates the concentration increases just enough to drop some out of solution. I'm speculating some here... carbonate chemistry is pretty complicated stuff because of the way (bi)carbonates interact with atmospheric CO2 and other acids or minerals in the tank.

I get a white film on the bottom glass too. I have assumed it was mostly bacterial film but some of it could be a precipitated mineral. When I look at it under the microscope I usually find protozoa there, so I wipe it off with my fingers or a little sponge while holding the siphon right nearby so it gets drawn out.

[RogueDiscus]

Thanks Dan. Always appreciate your insights. I do have very hard well water, around 450 ppm this time of year. I definitely get a fine grain particulate deposit, in addition to the usual film. I like the evaporation idea. Makes me think the consumption of the carbonates by the bio-load may not be too high, but I do like the idea that I have the natural buffer.