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confusing ph readings

1145 Views 5 Replies 4 Participants Last post by  boredatwork, 
B
My tank is still cycling, but I had tested my tap water a while back and the pH was around 8.0. I thought this was a lucky thing since I will be keeping cichlids which like high ph. Well, yesterday I tested the water in my tank and according to the reading its off the charts low. I am using an API test kit, so I think the lowest is 7.0 or something like that. My tank has a sand substrate, a lot of river rocks, a couple plants, and a cannister filter with foam and bio rings. Right now I am skeptical of the test kit, but its not expired and I tested three times in a row. Would the fact that its still cycling have anything to do with it? I am really confused, especially since I did a 75% water change last week, so how could the water ph drop so low so quickly?
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B
Even though I got so many replies last time :p I wanted to resurrect this topic.

After a little more attentiveness I have some better details on the situation.

The water out of my tap has a pH of 8.8. When I add it to my tank after about 75% water change, it goes to about 7.4 in a few hours and about 6.6-6.8 after about 24 hours. Its possible it will be even lower when I check again (I changed the water two days ago).

My tank has silica sand and a few plants. The filter has foam, biomax, and matrix in it. The rocks I use are mainly riverrock and slate. The rocks are my number one suspect, but they have been in there for about 6 weeks and I have done about 4 water changes with them in. I was thinking they had some concrete or something on them when I got them from the rockery - even though I washed them - but I would expect that to stop after several water changes. There are no fish in the tank yet.

I should also mention I have another tank that has small guppies in it. That tank is about 2 years old and it also exhibits the same pH drop, but only to about 7.0. It only has silica sand and 1 plant. No rocks. The filter just has foam in it.

Is it normal for the pH to change that much? I am worried about doing water changes when I have fish in it. Thats a big pH jump when I put the tap water in.
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E
I'm having a similar issue in my tank, and posted a question about it here a few minutes ago. I haven't had much luck getting responses here, but I sure hope someone responds to one of our threads - my dangerous pH drop is happening in a tank full of fish!
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J
PH fluctuates for a multitude of reasons, but yes it's normal for it to drop quite a bit depending on your local water chemistry and conditions in your tank. I don't have any experience with fishless cycling, but I have noticed some wild PH shifts when cycling tanks in the past. I would say for now just wait it out and when the cycle finishes then worry about the ph. Use a cichlid buffer and some limestone rock , crushed coral , or argonite in there to help buffer the water as well if the PH drops continue . The added carbonate source will go a long way to helping stabilize the the ph where you need it .
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Z
couple things. Let your tap water sit out (not in the tank) for several hours and then retest the pH. Water with a high level of CO2 can form carbonic acid after it sits, thus lowering pH.
Also, what is the alkalinity of your tap water and your tank. This will be the most important thing you can do to control pH swings is to maintain alkalinity.
check back with that information.
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Emory said:
I'm having a similar issue in my tank, and posted a question about it here a few minutes ago. I haven't had much luck getting responses here, but I sure hope someone responds to one of our threads - my dangerous pH drop is happening in a tank full of fish!
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Yea I just posted in your thread. After two days of reading I am embarrassed I asked the question - it must have seemed to obvious for most people! I am guessing thats why it didn't get any replies.

For future reference people with this problem should read this article I found. I found it extremely helpful in figuring out this mystery.

http://www.americanaquariumproducts.com/AquariumKH.html

Also, see the buffer recipe in the library to fix the problem.

http://www.cichlid-forum.com/articles/buffer_recipe.php
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