# questions about high pH



## charlieB (Aug 5, 2014)

Hello all, I am new to the "planted aquarium" world and since my first question here yielded such quick and helpful responses I am back again with another issue. To recap, I recently tore down one of my reef tanks and am in the process of converting it to a planted tank. It's a Biocube 29 gallon, lights have been retrofitted with high power LEDs and the wet/dry has been retrofitted as well. So you have the entire picture, I'll lay out everything in the tank at the moment. First, it has been running for a little over 2 weeks. There is ~70-80 pounds (3-4 inches) of 50/50 eco-complete and floramax substrate, about 15 pounds of Amazonite rock, 1 piece of Mopani wood (soaked for 2 weeks and was just added to the tank today) and the wet dry just has some coarse filter pad, a large wad of fine filter floss, some zeo/carb, and some bioballs. Since the tank has been set up I have been testing the pH daily and it consistently reads 7.6-7.8 (I have tested with both the low range and high range API test kits, comes out highest color on low range and lowest color on high range so I assume it somewhere in this range). This isn't a total shock to me based on its former use as a marine aquarium. When it was drained and cleaned it was scrubbed, soaked in concentrated vinegar solution for 5 days, scrubbed, soaked in dilute bleach solution for 24 hours, rinsed, scrubbed once more using concentrated vinegar solution, soaked in dilute bleach for another 2 hours, rinsed and air dried for 2 days. The same goes for all components (pumps, heaters, powerheads, etc). It was originally filled with tap water treated with Prime conditioner and has since undergone a series of 20-50% water changes alternating between RO/DI water and treated tap water. The RO/DI water pH tests at 7.0 with the same kits (obviously), and my tap water tests at 7.2 using the same kits both before and after conditioning. Regardless of massive water changes, the pH from the tank consistently reads 7.6-7.8. At this point I am just assuming residue/mineral deposits from the old system still exist in minute amounts and are constantly buffering the pH back up. My hope is that with time and many water changes this will balance out, and I have no problem with waiting, but if simply relying on time and water changes to fix the issue is futile I'd rather not waste my time. This is my first experience attempting to use an old marine system as a freshwater tank, so if anybody has any advice, or solutions that can help with my issue I am open to all suggestions and appreciate the help. I don't want to use additives or chemicals to lower the pH, as I don't want to fall into a cycle of constantly battling the rise in pH and subjecting the tank's inhabitants to a roller coaster of fluctuating water conditions. To be clear, there are currently no plants or fish in the tank. Thanks again, sorry if this post was too long but I wanted to be as thorough as possible so you planted tank geniuses can know all the information I have when formulating your response!

-charlie


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## TankAaron (Aug 8, 2014)

Jinx!

Hello Charlie. I'm sorry that I don't have any answers for you, however you may find this interesting. I just asked a similar question.

Perhaps our test kit "solution" cards are different. On mine, the High Range pH test color starts at 7.4, and the normal pH ends at 7.6. I do the same tests, also API, and get the same answer. That is why I was stating a pH of ~7.5.

However in my case, I have never used this aquarium for saltwater. Though it is my dream to someday have a reef tank, I've never had a saltwater aquarium. So, though this may not be a complete answer, it may be a piece to a puzzle. Whatever links your tank may have had to saltwater, it is probably not affecting any of the current results.

I doubt this has anything to do with it either, but I also used a water and vinegar solution to sterilize the tank. The tank remained filled with the solution for three days. Then I rinsed and kept it filled with water from the hose for a day. Then I let air/sun dry for a day.

I had the idea that some of the elements from the substrate, which can affect the pH may be causing this. However Seachem says the Flourite substrates, which I use, do not affect the pH.

Since you have no plants, I'm guessing you are not yet using fertilizer, and some my readings from the tests were from before I started dosing fertilizer. CO2 should only cause a drop in pH, however I'm also guessing you're not dosing CO2 since you do not yet have plants. Plus I was corrected on one idea I had. I use Excel. Though it is a carbon source, it is not CO2. So that wouldn't have an effect on pH either, though I realize CO2 lowers, and does not raise pH.

Hopefully any experts can piece these two together, and give us an answer. I also don't want to purposefully, and artificially alter the pH. And I only use RO water. I do not mix it with any other kind of water.


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## rjordan393 (Nov 23, 2012)

Surface movement of the water will raise pH; so will wet/dry filters. You can test for this using your ro/di water or tap water. Take about a gallon of either ro/di or tap water and add a powerhead to it and let it run for an hour and you will see an increase of pH. What you are experiencing is the normal rise in pH when water movement is exposed to air. 
A pH increase of 0.6 to 0.8 is not high at all. I would only be concerned if the pH increased above 1 unit.
If you are going to add plants and then later add a CO2 system, then I would suggest removing the wet/dry and replace it with a canister filter and install the discharge below the surface so that water movement at the surface is limited.
Anytime water is exposed to oxygen, pH will rise. But if there is enough CO2 in the water, then pH will drop. In marine systems, an ideal pH would be 8.2 to 8.4. But fresh water tanks usually run at 6.3 to 7.5 pH depending on if CO2 is added or not.
My tap water is 7.00 and I use CO2 injection. I have it set up to drop the pH down to 6.30 during the day. The reason for this is that plants during the day require CO2 to produce sufficient oxygen for the fish and the bio-filter. But at night, the roles are reversed and the plants do not use CO2 but take in oxygen. In most cases, there is sufficient oxygen to satisfy the bio-filter day or night. But I found that the normal oxygen level in my lightly planted tank is 6 ppm during the lighting period and by adding a power head at the surface of the water and run it after lights are out, I can increase the oxygen to 8 ppm. Now the reason I do this is to make the competition for oxygen less at night between the plants, fish and the bio-filter. Some have reported that their plants have benefited from this increased oxygen level.


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## Tugg (Jul 28, 2013)

A blanket statement of "aerating water will raise the pH" isn't necessarily true. It will cause gas exchange, which depending on your current CO2 and kH values will typically raise it. But it could also lower it in the case of fresh RODI water.

There are three components that have a huge effect on our pH values: CO2, carbonic acid, and carbonate ions (kH). They are also chemically related and try to maintain a certain level of equilibrium.

A small portion of dissolved CO2 binds with H20 and forms carbonic acid. This causes a lowering of the waters pH as it neutralizes the carbonate ions (also why Coke is acidic). RODI water that is permitted to sit and dissolve CO2 will typically gain an acidic pH (about 5.5) as it absorbs CO2. This specially filtered water has no kH offseting the carbonic acid to buffer the pH.

Most water sources have some degree of dissolved minerals that provide carbonate ions. The level is measured in degrees of kH (carbonate hardness). The presence of carbonates will buffer a waters pH up to about 8.3. This buffering offsets the carbonic acid from the CO2.

Wet/drys and other forms of surface movement promote a high degree of gas exchange. This causes the CO2 to leave the water as it saturates with O2 instead. When the CO2 is outgases, the kH in the water raises the pH back up. Water straight out of the tap is often low in O2 as organics and other biological organism have depleted it and instead produced CO2. Surface movement causes this CO2 to outgas, and O2 to become dissolved. The loss of the CO2 lowers the carbonic acid levels, raising the pH until a new equilibrium is reached with the carbonates.

Not accounting for other pH factors:
pH = 7 - LOG10(CO2/(3*dkH))

Aquariums naturally produce acids from the nitrogen cycle and other biological functions. I wouldn't worry about any residual minerals. If it's minerals, any remaining will slowly dissolve, and any effect they have on pH will gradually diminish. With this slow change, the tanks inhabitants shouldn't have any problems adjusting.

rjordan is spot on about a wet/dry with a planted tank. They make bad partners. That high level of gas exchange will push out all your CO2, and starve your plants for carbon. You can still have a sump, but look into submerging the drains and minimizing gas exchange. Herbie/Beananimal style overflows are a good choice since they're designed to keep air out. I like the extra water of a sump, and the conveniences they add to maintenance. Most people opt for canisters because they're easier.

In any case, there is a lot that goes into pH. For the most part, it's a moot point. As long as it's stable, your fish will be fine.


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## charlieB (Aug 5, 2014)

thanks so much guys


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## TankAaron (Aug 8, 2014)

Yes, thank you very much. And THANK YOU for providing that formula! I love formulas!

In my case, since I am not using CO2, and instead am dosing Excel, what would the effects be?

From what I remember reading on the Seachem articles, the Excel that ends up "clinging" to the leaves will then be used as a carbon source. Since the process of changing Excel into usable carbon takes place inside the plant, and not as a gas exchange in the water, will this not create carbonic acid? This part is only a curiosity thing.

My concern now is, should I remineralize the RO water to buffer pH fluctuations? Or will my plants, snail, and betta be okay?


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## Tugg (Jul 28, 2013)

You want to remineralize the water you use for water changes, but not the water used for top-off.


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