pH Keeps dropping. Is it a false reading on probe?

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JackBlasto

Aquarium Advice Freak
Joined
Apr 14, 2011
Messages
324
Location
Morgantown, WV
I just set up and planted my aquarium using a substrate called aquadurt. I have a PH probe that runs out of my sump back up to the tank and it keeps showing a steady drop of PH over time from when I put clean water in (7.9) from the tap which will drop to around (4.9) after about 8 hours. The guys at the pet store told me that the probe will give false readings until all the particles from the substrate settle. That the probe is reading the cloudy water and miscalculating the PH. How long should this last though? The tank looks relatively clear. It was planted yesterday and although it was indeed cloudy afterwards seems like these results should return to normal? It also seems crazy to me that me filling the tank with 7.9 water and it shifting to be that (4.9) acidic over and over is impossible. (I have done huge water changes three times before calling the store which was when they mentioned the high likelihood of false probe readings).

My concern is that 4.9 PH (if it is accurate) is too low for the plants. I need at least a ph of 6 and thus means I need to keep doing water changes. Any advice such as "leave it alone, it will return to normal readings in a week after settling"? ... or "Keep changing the water! It will kill those plants!" heh... Thanks.
 
Wow, that is pretty low. I am not sure I a buy a false reading on your pH probe. Are there any fish in the tank?
 
That's too low, and i don't think it's accurate. Maybe buying a test kit and trying it out?
 
It could very well be that low depending on the contents of aquadurt. But yes, confirmation with a liquid test kit would be good.
 
I'm doing water change now

No fish are in the tank so no worries there. Just trying to stay above 6 for plants as 5 is too low even for them for long periods of time I would assume? I confirmed the ph with a liquid test and it seems accurate. My only assumption is the substrate is turning my tap water acidic. I will keep doing water changes. Thanks. Any other advice feel free.
 
Yes, I agree - large, frequent water changes are in order until the pH stabilizes above 6.0. While most plants will survive in a lower range, you will have better luck with fish and plants if you can get it above 6.
 
Any yays or nays about using a store bought chemical buffer ? I realize its a general no no but wondering if in my situation it might be ok since there are no fish yet?
 
I wouldn't go that route. It is only going to temporarily mask the issue.
 
I think since you don't have fish, you have time on your side. Lots of water changes and some time for the soil to mature will probably raise the pH over time. I am not familiar with the substrate you chose, but have you looked around to see if this is a common problem with it? I know some planted substrates can have issues up front - for example Aquasoil leeches ammonia for the first few weeks that it is put in a tank.
 
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