# Troubleshooting low pH problem



## zubanhunter (Mar 22, 2011)

Hello,

Summary: freshwater planted tank has low pH. Tap water is basic. Water params normal (Aside from pH). Not sure of cause?

I have a relatively (<2months) new planted, 29 gallon freshwater tank stocked with only 9 cardinal tetras. Water parameters are mostly normal: Ammonia, nitrate and nitrite and chlorine are at 0. Water is slightly soft (75ppm gH).

My pH, however, is very low. Somewhere less than 6 (neither of my test kits go lower). My alkalinity is also low (~0kH). The tap water I am using comes out at close to 7.6 pH and 80ppm kH. I perform 2-3 10% water changes a week and the tank is fairly clean. I don't have any drift wood.

I have seen most people advising against worrying about pH since trying to mess with the pH can have unpredictable consequences; however, the pH is so low and drastically different than my tap water that I am concerned that there are other issues.

The substrate in the tank is a colored black gravel and I believe it may is a possible cause. When cleaning the tank, a fine black powder comes up from the gravel when I vacuum it. I took handful or so of the gravel, washed it very throughly in hot, chlorinated water and left it sitting in a bucket of treated tap water for 48hrs. After that time the pH was <6. A control bucket of the same size didn't change pH over the same time period. 

Is there any other probable cause that I should look into? Has anyone else had trouble with colored aquarium gravel lowering pH?

Thanks


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## phys (Feb 4, 2011)

I use RO water in my tank and also, I have low KH in my tank that causes a low ph. I've been using seachem's neutral regulator and now am using their alkaline buffer with it. Its stabilized so far with it. You can add some baking soda to bring up the KH but do it slowly testing and recording how much it takes to raise it. Its the KH that buffers the PH so if your KH is 0, then your ph is going to swing heavily. As i said, you can change your ph and KH as long as you do it slow enough. Too quick and you'll kill some stuff. 
Plants do take some KH and GH out of the water while they grow but not as much as you seem to be having. The fine black powder is stuff left over from the gravel, did you wash it before you put it in? That may be trapping some of the carbonate (KH) in your tank. So maybe rinse all of it. Drift wood may also help buffer the PH. Also, what kind of filtering do you have?


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## jrman83 (Jul 9, 2010)

You bring up your kh and you shouldn't have a problem. I wouldn't worry about trying to bring up your ph, your next water change will take care of that. Do you have a water softner on the house?


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## roacan (Dec 25, 2010)

zubanhunter said:


> I have a relatively (<2months) new planted, 29 gallon freshwater tank stocked with only 9 cardinal tetras.
> Thanks


According to this website, Cardinal Tetra Fish cardinal tetras likes a ph between 4.6 to 6.2

Maybe you should not worry about the ph, unless you want to add other fishes that needs a higher ph.


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## beaslbob (May 29, 2009)

Low pH is a direct result of carbon dioxide.

Removing the carbon dioxide will raise pH.

I use thriving live plants and the pH on all my tanks fw and salt are 8.4-8.8 with the api high range test kit. Even my fw tanks that had peat moss in the substrate.

In my marine setups I noticed that rasing kH helped prevent the nightly (lights off) pH drop but the just before lights out pH rose with just the addition of macro algaes.

my .02


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## zubanhunter (Mar 22, 2011)

Thank you for all the responses. To answer a few questions:

I have a biowheel filter (Penguin 200 rated for up to 50gal). I washed the gravel before using it, but during cleaning the gravel cracks very easily and then releases the fine black powder. 

I don't have a water softener. The low pH has persisted through many partial water changes [7-8 10% and 3-4 20%], although I have not done more than a 20% change at one time.

While the cardinal tetras seem to be doing quite well, I would like to add other fish in the future.



> Low pH is a direct result of carbon dioxide.
> 
> Removing the carbon dioxide will raise pH.
> 
> ...


My plants have been growing prolifically. If there is an excess of co2, its not likely from the fish. Would decaying plant matter be responsible? I have measured the pH of the tank before lights on, during the middle of the day, and just before lights out, but there doesn't seem to be any changes. 

Anyway, it seems that the best solution for now is to continue with frequent pwc and slowly add some baking soda to increase the kH?


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## jrman83 (Jul 9, 2010)

I would get a gh/kh test kit. Play around with testing and adding to get the range you want. You should shoot for the 3-5 range on kh, although 3 will suffice.


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## beaslbob (May 29, 2009)

zubanhunter said:


> Thank you for all the responses. To answer a few questions:
> 
> I have a biowheel filter (Penguin 200 rated for up to 50gal). I washed the gravel before using it, but during cleaning the gravel cracks very easily and then releases the fine black powder.
> 
> ...


Or perhaps just do nothing.

While the tank is getting established pH will be low then rise when the plants fully consume both the carbon dioxde and nitrates.

If your water changes are lowering nitrates the pH will be lower then if you had let the plants lower the nitrates.

So could be doing nothing will result in lower nitrates and higher pH from the plants.


my .02


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## zubanhunter (Mar 22, 2011)

> Or perhaps just do nothing.
> 
> While the tank is getting established pH will be low then rise when the plants fully consume both the carbon dioxde and nitrates.
> 
> ...


Do you have any good guides on leiden tanks?


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## beaslbob (May 29, 2009)

zubanhunter said:


> Do you have any good guides on leiden tanks?


There is some discussion on what exactly what a Leiden tank is but to me it is just plants maintaining the tank. the idea is the lack of other things just means more stuff is available for the plants which respond with vigor and help keep the fish as well. so the plants and fish balance each other out.

that said try dianna walstad's "ecology of the planted aquarium".

on more marine "dyanmic aquaria" by loveland and addey.

1979 Freshwater and marine aquariums articles (feb, oct nov) articles by Robert Gasser.

(all subject to my misspellings and feeble memory.)

or even here:

http://www.aquariumforum.com/f15/beaslbob-builds-reference-10056.html?highlight=beaslbob

And the beaslbob builds threads started here.

my .02


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## Socrates36 (Apr 28, 2011)

zubanhunter said:


> Hello,
> 
> Summary: freshwater planted tank has low pH. Tap water is basic. Water params normal (Aside from pH). Not sure of cause?
> 
> ...


Wow I am currently having the exact same problem and I have black coated gravel and purchased it from Petco. My pH is constantly dropping to 6.0 and after a water change I get it to 7.0 and just a few hours later it goes to 6.4. I have to do water changes every day and I can't keep up with it. Our tap water is soft and about 7.8 pH and it has 1.0 ppm ammonia in it so I use Prime but stopped using it for a couple of weeks in fear of it being the problem with my pH. I've been on another forum trying to figure this out. My tank is about 9 weeks old now and will not cycle. I read that lower pH hinders and stalls the process so it's been a nightmare! Yesterday I left out tank water in a cup overnight and tested the pH a day later and it didn't change so today I realized there's nothing wrong with the tap water but it's something inside the tank. So tonight I got a handful of gravel and left it in a cup of tank water and I am going to test the pH to see if it gets acidic overnight. It will be annoying to change gravel but I'm sort of hoping it is the gravel just so I can finally figure out what is wrong with my tank and fix it once and for all.


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## zubanhunter (Mar 22, 2011)

I just wanted to do a follow up since it looks like Socrates36 is having a similar problem. I re-did my tank and put in eco-complete gravel, completely replacing the old black colored gravel from petco. I no longer have any pH problems and my tank has cycled quite nicely!


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## Socrates36 (Apr 28, 2011)

zubanhunter said:


> I just wanted to do a follow up since it looks like Socrates36 is having a similar problem. I re-did my tank and put in eco-complete gravel, completely replacing the old black colored gravel from petco. I no longer have any pH problems and my tank has cycled quite nicely!


That's great! I am going to scoop it out today. I left a handful of gravel out in a cup overnight and the water's pH went from 7.0 to 6.6 so I finally know what is going on with my tank. I am going to replace the gravel with natural un-coated gravel as I'm a bit nervous about getting color coated gravel again! Hopefully the new gravel won't alter the pH. Thanks again for your reply.


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## phys (Feb 4, 2011)

Wow.. i have heard about this another time but after hearing 3 others have it, and having the same issue myself, i'm definately going to be changing my gravel. Maybe i'll do a beaselbob substrate build!


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