# Diluting Tap Water w/ RO to lower pH?

Dkonni
My current 36 Gal Freshwater Tank has a pH level of 8.2 - 8.4 which is high for these hybrid Goldfish that thrive in the 7.0 - 7.2 Range. My well water comes out of the tap at 8.2-8.4.

If I add a little bit of RO/DI Freshwater next water change, can you help me calculate how much proportionately should be added to dillute my Tap water, since it essentially Halves the pH with the RO being at 0?

Hypothetically, If I do a 10 gal water change & add 1-2 Gallons with RO water to help balance out the pH of the entire tank, can you help me determine exactly how many Gal of Tap water vs how many gal of RO water I should be doing in my 36 gal in order to drop the pH level by 1.2 - 1.4 ?
I guess I was wrong about pH level of RODI water & it not being 0.

maybe it’s 5-6 so I guess it would require more RO water to reduce my tanks total pH considering it doesn’t bring it down as drastically as I thought

Solution
Hey,

When I said my water is 0-0-5 I meant Amonia is at 0, Nitrites are at 0, and Nitrates at 5.

but the breeder I bought these Ranchu said my water needs to be 7.0 - 7.2

This sounds like you're mixing up Nitrates, KH and pH?

Nitrates have absolutely nothing to do with KH and pH.

The triangle here is pH, KH and CO2

Lower KH or more CO2 = lower pH
Higher KH or less CO2 = higher pH
Since you don't use CO2, your only (and the best) way of influencing pH is KH.

To profoundly give you numbers, we need to know the KH of your tap water. With your pH being that high I would guess it around the 12 - 20 range. But as said, we need numbers!

Are you adding anything to the water? Like salt or something?
Frank the Fish guy
To go from a pH of 8.3 down to 7.1, you need to go down by 1.2.

But pH is a logarithmic scale, so this is a factor of 10^1.2 = 16

So you need 16 parts RO water to 1 part of your well water.

So that would be

X + X/16 = 36 gallons

X(1+1/16) = 36

X= 34 gallons of RO water

and 2 gallons of well water

Dkonni
To go from a pH of 8.3 down to 7.1, you need to go down by 1.2.

But pH is a logarithmic scale, so this is a factor of 10^1.2 = 16

So you need 16 parts RO water to 1 part of your well water.

So that would be

X + X/16 = 36 gallons

X(1+1/16) = 36

X= 34 gallons of RO water

and 2 gallons of well water
Oh wow! I didn’t realize how much would have to be RO water. That is probably not ideal considering the RO water doesn’t have all the beneficial minerals or requirements that dechlorinated tap has

ruud
The equation is of course a little more complex. If you dilute to such an extend, the KH will drop also. I'd forget about pH and measure KH instead. I expect you need to dilute less in order to achieve the desired pH range, due to the drop in KH.

Dkonni
The equation is of course a little more complex. If you dilute to such an extend, the KH will drop also. I'd forget about pH and measure KH instead. I expect you need to dilute less in order to achieve the desired pH range, due to the drop in KH.
Thanks for all the help. But, What would your recommendation be? My tank is at 0,0,5 but pH is always super high. I’m just trying to get it to a safe enough level for these sensitive Ranchu.

how many gal would you dilute with RO to try & manage?

ruud
My tank is at 0,0,5

I have no idea what this means

I don't know what the ideal parameters are for Ranchu. Find out what the preferred GH and KH values are. Find out what you currently have in your tank. Next, prepare water for your usual water changes that have the ideal GH and KH values. Or if required, the KH at the lower end. After a while the GH and KH match with those in the tank.

Once this happens, test your PH. My bet is that it has dropped to at least 7.8. Due to life inside your aquarium, the pH will drop further to neutral grounds. And it will, because I expect your new KH to be lower, giving room for a further decrease.

Dkonni
I have no idea what this means

I don't know what the ideal parameters are for Ranchu. Find out what the preferred GH and KH values are. Find out what you currently have in your tank. Next, prepare water for your usual water changes that have the ideal GH and KH values. Or if required, the KH at the lower end. After a while the GH and KH match with those in the tank.

Once this happens, test your PH. My bet is that it has dropped to at least 7.8. Due to life inside your aquarium, the pH will drop further to neutral grounds. And it will, because I expect your new KH to be lower, giving room for a further decrease.
When I said my water is 0-0-5 I meant Amonia is at 0, Nitrites are at 0, and Nitrates at 5.

but the breeder I bought these Ranchu said my water needs to be 7.0 - 7.2

due to this being kind of an immediate problem, should I buy Seachem Neutral Regulator to try \$ chemically change the water to a lower pH or just dilute as much RO water as I can

ruud
I'm the last person on this forum to discuss ammonia/nitrates, or Seachem products, or a lot of things actually.... sorry about that.

I also don't understand the emergency, but if you feel it is, because the breeder told you, I'm not going to argue, and agree with your solution regarding diluting with RO water. Use 100% RO water, just change modestly, because we, or at least I, don't know anything about your water parameters (except what the pH was according to one point in time).

I would also purchase minerals to be used for RO water. You need to investigate what works for Ranchu fish.

The thing to keep in mind is that your pH is high because of your KH. So you also need to figure out why your KH is high. What is the KH in your tap? Or is it caused by certain media you are using. If the KH in your tap water is low (and it is some media that is causing this), than you don't need minerals, but rather dilute your tap water with RO water in the future. Or not even at all. Remove the media (if that causes the problem) and your problems are solved.

Hope this helps a bit.

Zer0Fame
Hey,

When I said my water is 0-0-5 I meant Amonia is at 0, Nitrites are at 0, and Nitrates at 5.

but the breeder I bought these Ranchu said my water needs to be 7.0 - 7.2

This sounds like you're mixing up Nitrates, KH and pH?

Nitrates have absolutely nothing to do with KH and pH.

The triangle here is pH, KH and CO2

Lower KH or more CO2 = lower pH
Higher KH or less CO2 = higher pH
Since you don't use CO2, your only (and the best) way of influencing pH is KH.

To profoundly give you numbers, we need to know the KH of your tap water. With your pH being that high I would guess it around the 12 - 20 range. But as said, we need numbers!

Are you adding anything to the water? Like salt or something?

ProudPapa
Goldfish live for years outside in my cattle troughs in my 8.2 pH water. While I wouldn't argue that 7.0 or a little higher might be ideal, I'm skeptical of any claims that they need it precisely there.

ruud
Hey,

This sounds like you're mixing up Nitrates, KH and pH?

Nitrates have absolutely nothing to do with KH and pH.

The triangle here is pH, KH and CO2

Lower KH or more CO2 = lower pH
Higher KH or less CO2 = higher pH
Since you don't use CO2, your only (and the best) way of influencing pH is KH.

To profoundly give you numbers, we need to know the KH of your tap water. With your pH being that high I would guess it around the 12 - 20 range. But as said, we need numbers!

Are you adding anything to the water? Like salt or something?

You found the solution!

Anyways, nitrification affects pH. There's always a relation

Zer0Fame
Hey,

true, but if you have a significant pH/KH drop because of nitrification, you have a very different problem.
What's the english word for a sudden, huge drop because of nitrification? In German it's "Säuresturz" which roughly translates to acidity collapse?

ruud
2 H+ for every NH4 molecule...

As 10 H+ molecules can result in the same pH as 1000000000000 H+ molecules, those 2 H+ have significant effect in the first case, but not in the second.

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