Best method for water changes when tap water has drastically higher pH than tank water?

Stykk

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Hey everyone,

I'm beginning a new planted tank, and using Fluval Stratum as the substrate, which it claims should buffer my water's pH down to 7 or 6.8ish. However, my tap water is usually around 8 or a little higher. Instead of just pouring fresh water into the tank, what's the best method to do my weekly water changes when there will likely be such a drastic difference between the water in the tank and the water coming from the tap? Do I need to treat the water, mix it with R/O or distilled? Any ideas greatly appreciated.
 

DaveWatkin

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Could look at using seachem acid buffer right before putting into the tank so it goes in at the right pH. This will wear off over time but the substrate should hopefully take over from there to keep things smooth (never used it so not sure on how it works). Acid buffer will lower KH to achieve its pH though so might want to take that into consideration.

On the other hand if you just always use your tap water the water and substrate might develop an equilibrium somewhere in the 7's and adding water at water change would only cause a slight fluctuation for a short time so no big deal.
 

dw1305

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Hi all,
However, my tap water is usually around 8 or a little higher
Do you know the alkalinity (carbonate hardness (dKH)) of your water? If you have a <"TDS (conductivity) meter">? That value would be useful too. You can really only interpret the effects of pH changes if you know how they relate to changes in water chemistry.

Active substrates work by <"ion exchange">, where they swap an H+ ion for another more abundant, more strongly bound, cation in the water column, often a calcium (Ca++) ion. pH is a ratio H+ ion donors (acids) and acceptors (bases) and you've added H+ ions and the pH falls.
Could look at using seachem acid buffer right before putting into the tank so it goes in at the right pH. This will wear off over time but the substrate should hopefully take over from there to keep things smooth (never used it so not sure on how it works).
Because pH and buffering are quite <"complicated subjects"> it gives an opportunity for the unscrupulous to mislead, for me it is a way of <"transferring your money to Seachem">, but after that I'm struggling.

cheers Darrel
 
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DaveWatkin

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I currently use equalibrium and alkaline buffer to get my water where I want it (6dGH, 4dKH). I was using acid to try and lower pH but realised it was a bit of a con so stopped and now live with the pH that alkaline buffer provides. Starting CO2 injection now so will lower that way.

I'll look into replacing the alkaline buffer when my stock runs out. Do you think equalibrium is also not worth the cost and do you recommend an alternate?

Thanks for the input. Sorry to hijack the post a little Stykk!
 

tam

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I presume the tank was originally filled with the same tap water? If you are worried just do a couple of smaller changes inside of one big one :)
 

Witcher

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Hey @Stykk There is absolutely no reason for worrying or keeping pH stable in the tank - it changes very quickly in natural waters (and in aquariums) depending of few factors - temperature, amount of CO2 exhausted by bacteria (which are consuming detritus, plants, ferts etc.), levels of oxygen caused by plants and other tank inhabitants. All you need to worry about is stable water hardness (it very rarely changes in the nature apart from floods, rain seasons etc.) and relatively stable amount of ferts (which again changes in the nature periodically, and it's caused by floods etc.).
 

rebel

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I wouldn't bother and just dump it in. Use an active substrate though like ADA, tropica etc for your plants. Just match the TDS roughly.

Usually water pH is high due to liming so it's not really high hardness anyways.

My rainwater is 10 TDS and tank is 135. I just dump it when doing 60% water changes and add some GH back (DIY gypsum/MgSO4 but you can buy seachem equilibrium).
 

dw1305

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Hi all,
I currently use equalibrium and alkaline buffer to get my water where I want it (6dGH, 4dKH). I was using acid to try and lower pH but realised it was a bit of a con so stopped and now live with the pH that alkaline buffer provides.
Yes, that is right, the acid would lower the pH by removing the carbonate buffering (converting HCO3- to CO2) so you are giving with one hand (adding the alkaline buffer) and taking away with the other (by adding the acid).
I'll look into replacing the alkaline buffer when my stock runs out. Do you think equalibrium is also not worth the cost and do you recommend an alternate?
Seachem won't tell you <"what is in their buffer"> or <"Equilibrium">, but it will be some combination of cheap and readily available salts. I'd be reasonably confident that the alkaline buffer will be sodium bicarbonate (NaHCO3) based, this is because only the carbonates of alkali metals are soluble in water and NaHCO3 is extremely cheap to buy. Adding sodium isn't ideal for planted tanks, so they also offer a "sodium light" option for planted tanks in "Equilibrium".

You can raise both dKH and dGH with a calcium carbonate (CaCO3) based source. I usually suggest <"oyster/cockle shell chick grit">, but a bit of cuttle "bone" will also do, you can get these really cheaply from ebay etc for caged birds. You might also be able to PYO if you are close to a beach?

Calcium carbonate technically <"isn't soluble in water">, but it is in weak acids, and <"water containing CO2 is a weak acid">.
Starting CO2 injection now so will lower that way.
This is another strange one, when you add CO2 you don't lose any alkalinity, you've added more Dissolved Inorganic Carbon (DIC/TIC) and you just changed the pH value in the <"HCO3- ~ CO2 buffering system">.

If you just want to raise dKH you can use potassium bicarbonate (KHCO3), again you can buy this cheaply as "food grade" via ebay etc. Have a look at James' Planted Tank <"re-mineralising agent..."> for some more details of ways of raising dGH and dKH.

cheers Darrel
 
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