PH Help please?

  • #1
Hello, I have just started cycling my tank again and have some questions about ph. Straight out of the tap the reading is 7.0 to 7.2 which I understand to be normal. However, my tank water appears to be off the chart for both normal PH and high range. I have attached photos, the normal PH is a pretty deep blue, and the high ph a pinky burgundy. I am confused! What is my PH? I want to put 3 guppies in my 10 gallon tank once cycled. It has a gravel substrate, artificial rock, 3 real rocks bought from the fish shop and thoroughly cleaned and 2 fake plants. I have added the appropriate dose of API Stress coat, QuickStart and aquarium salt. It's been going a couple of days, NH3 1ppm, NO2 2ppm and temp is 25c or 77f. Also do I need to get a hardness test kit?

Thanks in advance!
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  • #2
I wouldn't trust the test results out of the tap, it likely is similar to the one in your tank. You need to let it sit for 24 hours before testing the sample of tap water for it to be accurate.

Your tank water if it is that high is fine, almost all aquarium fish are fine in high pH unless they are wild caught. It's easier for fish to adapt to a higher pH than a lower one.
  • #3
Chemistry lesson incoming:

CO2 is an acidic gas and is the reason we have things like acid rain. It occurs over densely populated regions where there is excess CO (carbon monoxide) and CO2 (carbon dioxide).

A lot of municipal water treatment plants today are using CO2 injection when treating water when they have large amounts of calcium carbonate in the water. The calcium mineralizes to the components in the treatment plant reducing its effectiveness and ability to properly treat waste water.

The injection of CO2 creates carbonic acid which binds to the minerals in the water creating carbonates and by-carbonates which are more controllable. It also reduces the PH of the water creating a more neutral environment.

The downside to this for aquarists is the excess CO2 will off-gas (release the excess) when exposed to normal atmosphere conditions which contain a lower concentration of CO2, this reducing the acidification properties and returning the water to its natural state.

Some homework you should do is full up a bucket or jug with water and test it over a period of time to determine how long it takes for the PH to normalize. Test it immediately, and every 6 hours until it no longer changes. Post your results here when you have them.

Also do I need to get a hardness test kit?

If you can, yes. Like G.I. Joe said "Knowing is half the battle."
  • #4
HI there,

Your Guppies are freshwater fish that do not require salt, and the aquarium salt may be impacting the PH issue. I would stop using it. If you want to do a truly brackish tank down the road I would use a complete salt, a marine salt like Instant Ocean. If you intend to do brackish then I would get a brackish hydrometer and monitor your salinity so you don't end up full saltwater with freshwater fish. In my brackish setup I use Instant Ocean, and on the hydrometer I keep it between 1.004-1.006 easily with just a teaspoon of marine salt per gallon of water replaced. This I do for my Molly fish.

I would do daily water changes for the next week, 25% even though you are cycling. I would not add any more positive microbe products. I would get a product like PH down and use it and retest until your PH is under control. After you've got it in the right range for a couple of days don't add anything or do any more water changes and continue to cycle. Then retest, and see if you are stabilized.

Personally I don't use tap water. I only use prepared fish water like eLive, or bottled spring in the right range for the particular fish. That's my preference. Less Koodies to deal with and no chlorine.

There are other factors that can influence the PH such as live plants and natural rock, read into that. In my aquariums I am careful to use only natural rock, coral or shells, or glass or crystal or plastics, no fabrics, no resin items, nothing that can mold, corrode or rot.

Good luck!
  • #5
Before you add anything to your water read my post. Maintaining water chemistry is very difficult to keep right until you understand the chemistry of the water your using. The first step you need to take is to learn about your source water.
  • Thread Starter
  • #6
Thanks for the very helpful responses, I will do the PH test as suggested and then come back to you.
  • #7
Hi, Do not use PH down or any PH modifiers. I read your PH at about 8.3 , brighter than 8.2, but not purple like 8.4.

I agree that the reason your ph rises is most likely due to CO2 in your source water. Keep your water changes to 50% or less if determined its a full point apart (7.2-3 to 8.2-3). I usually tell people to keep the net ph difference at .5 or less during a water change to minimize stress to their fish.
Your other option is to put an airstone in a bucket of water for water changes. This will naturally off gas the CO2 and let the ph rise to its natural state.

I agree your tank does not need aquarium salt.

If you are fishless cycling I would keep using the bacteria from Quick Start to cycle faster.
  • #8
Few points to add:
Guppies are naturally brackish water fish, they are fine in freshwater, thrive in slightly salty water. And aquarium salt do not affect pH.
I am not aware that water plants are injecting CO2. In fact, they add chemicals to increase pH (corrosion inhibitors) since acidity is bad for pipes. Cold water under pressure from tap has more air dissolved (more CO2 as well) therefore it has a lower pH than your tank.
CO2 does not modify the amount of carbonate/ bicarbonate in the water (carbonic acid is a weak acid), I would say it is the other way around: a water high in carbonates can "hold" more CO2.
Main acid rain gases are Sulfur dioxide and Nitrogen oxide. With water, they form Sulfuric acid and Nitric acid, much stronger acids than Carbonic acid.

I agree that you should measure tap water pH after the water has been de-gassed. If it is still a lot different than your tank, I'd look at the rocks, substrate and decorations and see if anything is "targeting" your pH
  • Thread Starter
  • #9
Thank you for that very clear, and the air stone idea seems a good one.

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