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*** been cycling my tank w/ ammonia and I only have pool filter sand and holey rock in it. The PH has always been 8.4. I check the water daily. My tap water straight out of the faucet was 8.2-8.4 when I filled up my tank back on Dec. 27, '10.

Fast forward to tonight I added 5 more large holey rocks to my tank so I redid all the rock work. I took out 5 gallons of water to keep the little rocks that were already in my tank in and when I was done I filled the tank back up w/ 5 gallons of water from my faucet. I added less than 1ml of Prime and 3mls of ammonia since it was at 0 for 24hrs. now.

I let the tank chill for about 2 hours and I took some water readings. The ammonia was less than 1ppm, the nitrites were 5ppm+, nitrates were 5ppm but my PH was 7.6? I though it was a fluke so I checked it again and it was 7.6. I though maybe it was the new rocks but then I checked my faucet water and it was 7.4? I doubled checked it and it was 7.4?

What would cause a large drop in PH? I only added 5 gallons of water with a PH of 7.4 so I dont see how that wouldve lowered my tanks PH which was at 8.4.
 

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The pH levels of tap water are usually within a certain range so you won't see the same readings every day if you measure it. Rocks and substrate have minimal impact on raising or keeping pH levels stable if your tap water is already alkaline (depending on what type of rocks or substrate you have, they can help more if your tap water is acidic - i.e pH below 7.0). Adding a buffer (like baking soda) to raise your kH will help raise and maintain your pH above 8.0. A lot of people on this forum will tell you not to tamper with your tap water but if the variation you get out of the tap is as great as yours I'd want to stabilize it.

The bacteria converting ammonia and nitrites produces acid as a byproduct which also lowers pH so pH fluctuations can be fairly typical during the cycling of a tank even if you're not getting variations out of the tap.

Here's a good article from the library on the topic.

http://www.cichlid-forum.com/articles/w ... mistry.php
 

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I've been cycling my tank w/ ammonia and I only have pool filter sand and holey rock in it. The PH has always been 8.4. I check the water daily. My tap water straight out of the faucet was 8.2-8.4 when I filled up my tank back on Dec. 27, '10.
but then I checked my faucet water and it was 7.4? I doubled checked it and it was 7.4?
Might want to give your water company a call.

Robin
 

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zimmy said:
The pH levels of tap water are usually within a certain range so you won't see the same readings every day if you measure it. Rocks and substrate have minimal impact on raising or keeping pH levels stable if your tap water is already alkaline (depending on what type of rocks or substrate you have, they can help more if your tap water is acidic - i.e pH below 7.0). Adding a buffer (like baking soda) to raise your kH will help raise and maintain your pH above 8.0. A lot of people on this forum will tell you not to tamper with your tap water but if the variation you get out of the tap is as great as yours I'd want to stabilize it.
+1

Tap water pH fluctuations are usually due to differing amounts of dissolved CO2. The more (in the form of carbonic acid) the more acidic. There is also a second order temperature effect. The lower the temperature the lower the pH. And both effects are correlated.

Try letting the tap water sit / age for a day or so and let it come up to the same temperature as your tank. Test then. I'll bet the pH of the tap water will be higher.

Using a buffer will level out pH fluctuations and if you add/replace the same amount of buffer every time you do a water change your pH will indeed be more stable. I did this for years.

However, after using a controller that measures and records pH and temperature every 15 minutes, I've observed that my pH fluctuates daily by 0.2 units as my temperature varies from "lights out" to "lights on" by 2 degrees F. My point being that observation of tank conditions is an important part of serious fish keeping, but one should be reluctant to control things that in the end don't matter.
 

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What part of Texas? Reason for asking is to try to figure if you have the same situation as I have. My water supply is drawn from different sources. Some from the river which is pumped to fill a lake to maintain water supply and some from wells. This can make the water vary depending on which you are getting more of. I should think that your water does not need more buffer in either case due to the heavy limestone in much of the area. That may not speak for your area, though.

It could also be a case of the water supply needing to fight and algae bloom or such and using different treatment. Their primary requirement is safe water and sometimes that conflicts with what we want as fishkeepers. If you call, the reaction you get may vary quite a lot. Sometimes cordial, sometimes hostile, so tread carefully there.
 

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What would cause a large drop in PH? I only added 5 gallons of water with a PH of 7.4 so I dont see how that wouldve lowered my tanks PH which was at 8.4.
The instablility of pH can be due to a low KH, or buffers, that's been mentioned in some of the previous posts. CO2 also comes into play as pH, KH, and CO2 are all inter-related in some manner. Test your KH (sometimes called carbonate hardness) of both tap and tank. If it's low, like <5, then develop a plan to add sodium bicarbonate (baking soda) to bring it up. The tank water KH will most likely be lower than tap and that would be due to the nitrification processes. The end result is acidic and consumes buffers, lowering KH. The rocks had nothing to do with the pH drop, and can actually help buffer, but over time.

See Practical Water Chemisty in the forum library for a good, basic explanation of how KH and pH go hand in hand.
 
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