High tap ph making water changes difficult - The Planted Tank Forum
 
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post #1 of 6 (permalink) Old 03-22-2019, 10:57 PM Thread Starter
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High tap ph making water changes difficult

So I have a high tech 75g tank with co2 injection and aquasoil. Between the co2 and aquasoil, it is bringing my ph down to around 6.6.the trouble is my tap water comes out off the charts hard even on the high range ph water test kit, so it is 8.8 or higher. I gassed off a glass of water for a few days and it came down to 8.6 but it is still high. The trouble is with water changes, anything over a 40% change is stressing the fish. I try to do it in the morning before the co2 comes on and I have tried added the water back very slowly, but sometimes I still see signs of stress.

I know the concensus is not to mess with the ph, and also know that if I was, it would be best to mix it with RO water. But we just had a baby and it will be a while before I can afford a RO system.

Could I for the time being pre treat water in a separate tube with vinegar and do the water changes with that? If I could figure out how much it would take to lower it, I could add a set amount of vinegar to the tube each time, so it stayed consistent. Does anyone know a reason why this wouldn't work? My kh is about 9 if anyone needs to know. Thanks!

Bump: Also I have been having a lot of trouble with water cloudiness with the aquasoil. I read that the early versions of aquasoil would cloud the water when paired with high ph water. Can anyone confirm that the newest version has that problem fixed?

Last edited by Dirtdawg57; 03-22-2019 at 11:04 PM. Reason: Typo
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post #2 of 6 (permalink) Old 03-23-2019, 03:36 PM
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How long has this tank been up and running? How frequently do you do water changes?

Basically, the soil has the ability to buffer pH down to the mid-6's, and part of this is done by stripping KH from the water. This buffering ability gets depleted over time, and the amount of time this takes depends on how much carbonates you are adding to the tank.

Long story short, you always want to do RO with buffering substrates if you want to keep the buffering ability. But since that isn't an option, you have to choices: 1) Deplete the buffering ability, 2) Lower pH of tap by other means.

I don't like the idea of depleting because you lose a lot of benefits like low pH making ammonia ammonium which is less toxic for fish. It also makes some nutrients more available to plants.

To deplete the buffering, add maybe 1-2 grams of baking soda (sodium bicarbonate) daily to your 75G tank. This will raise pH slightly, and the soil will attempt to strip it from the water column. Keep an eye on pH as it raise faster than the soil can keep up, and you want to know when the soil stops stripping KH.

To lower pH, RO would be the usual way to go, but that does require an initial investment to pay off. Instead, you can use peat with your water change water, but it does leech tannins and color your water. I'm not sure what else has the ability to strip KH without leaving tannins.

As to cloudiness, it's probably due to high KH in your tap. That issue would probably go away if you did either of the above.
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post #3 of 6 (permalink) Old 03-23-2019, 07:08 PM Thread Starter
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Originally Posted by natemcnutty View Post
How long has this tank been up and running? How frequently do you do water changes?

Basically, the soil has the ability to buffer pH down to the mid-6's, and part of this is done by stripping KH from the water. This buffering ability gets depleted over time, and the amount of time this takes depends on how much carbonates you are adding to the tank.

Long story short, you always want to do RO with buffering substrates if you want to keep the buffering ability. But since that isn't an option, you have to choices: 1) Deplete the buffering ability, 2) Lower pH of tap by other means.

I don't like the idea of depleting because you lose a lot of benefits like low pH making ammonia ammonium which is less toxic for fish. It also makes some nutrients more available to plants.

To deplete the buffering, add maybe 1-2 grams of baking soda (sodium bicarbonate) daily to your 75G tank. This will raise pH slightly, and the soil will attempt to strip it from the water column. Keep an eye on pH as it raise faster than the soil can keep up, and you want to know when the soil stops stripping KH.

To lower pH, RO would be the usual way to go, but that does require an initial investment to pay off. Instead, you can use peat with your water change water, but it does leech tannins and color your water. I'm not sure what else has the ability to strip KH without leaving tannins.

As to cloudiness, it's probably due to high KH in your tap. That issue would probably go away if you did either of the above.
Thank you for the tips! I rebuilt the tank about 2 months ago with aquasoil, but it had an established canister filter. I did really want to keep the buffering ability and that is one of the reasons I went with the aquasoil.

So I assume you would not agree with mixing distilled vinegar in a separate tub for the time being?

I guess I better start saving for a RO system. Does anyone have any recommendations for a decent system that could handle weekly water changes for a 75g?
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post #4 of 6 (permalink) Old 03-24-2019, 01:30 AM
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Distilled vinegar would not be my choice of an acidifier. It's not that strong an acid, it smells -- which means it won't stay permanently in the tank -- and some organisms will actually consume it over time.

On the other hand, it's cheap and safe to work with.

If you are comfortable working with strong acids, some muriatic acid (hydrochloric acid) from your hardware store is not too expensive, is much more powerful, and goes to chloride in your tank, which is harmless, odorless, and not much consumed by tank residents. I used hydrochloric acid routinely to acidify my rather alkaline local tap water back when I was keeping discus. In fact, I still have some of the bottle after twenty years, which I occasionally use for other purposes.

A middle ground is sodium bisulfate, which is sold for use in pools and spas to bring pH down. This assumes you can tolerate a bit more sodium in your tank. Sulfate is pretty innocuous, being a plant nutrient that is not consumed rapidly.

If you decide to acidify, regardless of the acid chosen, don't overdo it. You shouldn' try to bring the pH below about 7.5 in water equilibrated with air. (Lowering it further with carbon dioxide injection is fine.) Also, if you add acid to a bucket of water until its pH is 7.5, you'll come back the next day and it will be back up to 8 as the water re-equilibrates with the air. It will take some experimenting to find the right dose to get it down to 7.5 for good, and you'll get it downright acid before it equilibrates to 7.5. So you probably don't want to acidify as you're adding to your tank unless you do frequent small water changes. Acidify in an aerated bucket and let sit overnight before doing the water change.
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post #5 of 6 (permalink) Old 03-24-2019, 03:28 AM Thread Starter
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Originally Posted by kgbudge View Post
Distilled vinegar would not be my choice of an acidifier. It's not that strong an acid, it smells -- which means it won't stay permanently in the tank -- and some organisms will actually consume it over time.

On the other hand, it's cheap and safe to work with.

If you are comfortable working with strong acids, some muriatic acid (hydrochloric acid) from your hardware store is not too expensive, is much more powerful, and goes to chloride in your tank, which is harmless, odorless, and not much consumed by tank residents. I used hydrochloric acid routinely to acidify my rather alkaline local tap water back when I was keeping discus. In fact, I still have some of the bottle after twenty years, which I occasionally use for other purposes.

A middle ground is sodium bisulfate, which is sold for use in pools and spas to bring pH down. This assumes you can tolerate a bit more sodium in your tank. Sulfate is pretty innocuous, being a plant nutrient that is not consumed rapidly.

If you decide to acidify, regardless of the acid chosen, don't overdo it. You shouldn' try to bring the pH below about 7.5 in water equilibrated with air. (Lowering it further with carbon dioxide injection is fine.) Also, if you add acid to a bucket of water until its pH is 7.5, you'll come back the next day and it will be back up to 8 as the water re-equilibrates with the air. It will take some experimenting to find the right dose to get it down to 7.5 for good, and you'll get it downright acid before it equilibrates to 7.5. So you probably don't want to acidify as you're adding to your tank unless you do frequent small water changes. Acidify in an aerated bucket and let sit overnight before doing the water change.
Good info! Thanks!

So after some research of ro systems, I am getting mixed signals. Most everyone recommends ro water to reduce ph in aquariums, but a lot of reviews I read from people that have them said they only reduced the ph by .2 points.

So would you have to use the ro to reduce the kh and then use muriatic acid to bring the ph down? I am trying to refresh on the chemistry of it but it has been a while.

Last edited by Darkblade48; 03-24-2019 at 11:58 PM. Reason: Please use the edit function for back to back posts to keep threads cleaner
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post #6 of 6 (permalink) Old 03-25-2019, 12:45 AM
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Originally Posted by Dirtdawg57 View Post
Good info! Thanks!

So after some research of ro systems, I am getting mixed signals. Most everyone recommends ro water to reduce ph in aquariums, but a lot of reviews I read from people that have them said they only reduced the ph by .2 points.

So would you have to use the ro to reduce the kh and then use muriatic acid to bring the ph down? I am trying to refresh on the chemistry of it but it has been a while.
Mixing with R/O water should bring both pH and dKH down, since they are linked:

pH = 7.0 + log dKH

where dKH is carbonate hardness in German degrees and we're assuming well-aerated water without carbon dioxide injection. However, the log in the formula does mean that the pH change will tend to look smaller than the dKH change.

If you can afford to R/O enough water to mix with your tap water and bring its pH down to something reasonable, that's better than acidifying. If your tap water has pH 8.6, that means dKH must be about 40 dKH, which is pretty spectacular. (Ever think about keeping Lake Malawi cichlids?) Lowering it to 10 dKH will bring the pH down to about 8.0, while 5 dKH will bring it down to 7.7, which is about where my own tap water is at. I don't do anything to modify my dKH except injecting carbon dioxide. But that means you are not so much diluting your tap water with R/O as you are hardening your R/O with tap water! Which is fine if you can afford the R/O.
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