Why is my pH higher than the source water?

adeire

AC Members
Jul 25, 2010
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Norfolk, VA, USA
I hope someone can help me out with this. I add 50/50 spring water and RO water. The spring water has a pH around 7, the RO is around 6.4, but the water in my tank is 7.6+ (test doesn't measure higher). I just transferred & upgraded this tank from a 20L (kept by my father) to a 29 gallon at my house, and he didn't test water quality, so I don't know the history there. He says he added 10/90 spring water & RO water. The tank is planted with Vals and java moss, a mix of gravel & sand substrate, sponge filter, no CO, and I have 2 airstones. Fish are 10 Flame Tetras and 7 Neon Tetras.

Last testing had ammonia 0, nitrate 20, kH 5. I want to have a pH right at or under 7, and certainly not higher, and I don't understand why I don't have that. I tried turning the airstones off for a few hours, but it didn't have any effect. I even added some crape myrtle leaves, but no effect. There is a very large piece of driftwood, too, but it's been there a couple of years.

This tank was originally mine, then given over to my father when I moved out, and now we have (finally!) moved it in with me. I would like to add some corys & shrimp, but I want to settle the pH issue first. So, any ideas? Thanks in advance...
 
What kind of test kit? Liquid or dip strips? Why are you using spring water and RO? What are your readings on your tap water? Shouldn't be any need for a special pH with the fish you are keeping....
 
liquid API tests. I wasn't using tap water b/c my parents had a water softener system at their house and I didn't want to use that. I haven't checked my tap water, I'm just using what the fish are used to. My dad is perfectly willing to supply RO water. :) I don't NEED a low pH, but with the water I'm adding, it SHOULD be a low pH. :/ The fishies seem perfectly happy & healthy, so that's not a problem, but I don't want to add without knowing why it's high or if it's going to drop.
 
I'd test your tap, on a sample that set out overnight in a shallow dish..see what it's pH KH/GH is and do small changes to bring your tank to those conditions.
 
I'll test it. You think there's something with the water I'm adding now pushes the pH up? I thought if anything the tank water would be lower than the source water.
 
7+ is actually good for shrimp, what do you add to the water? Also if your sand is aragonite it'll push the ph up a bit, so will some rocks. I use RO in my one planted with shrimp they seem to breed better then when I was running tap, however you should use something like equilibrium with the RO since its had alot of its minerals stripped out of it.
 
Hmm, I've never added anything to the water. The original plan (2+ years ago) was to use the RO water with the Spring water at the right ratio to get a slightly soft, slightly acidic tank. With driftwood, plants, leaves, even some peat in the filter to be a little like an SA biotope. And that worked well - the Flame Tetras were breeding, I had Cherry shrimp which were also breeding, a generally happy tank. :) Then I moved out and it's been over a year since I've been, um, in charge of the tank, so now that's it is in MY house, I'm trying to get on top of everything and get back to how it should be (not that my dad neglected it, it just needs a little TLC). The sand & rocks are from Petsmart two years ago, nothing fancy, but I don't remember any specifics.
I have some hardy little fish now, but Shrimp can be more delicate, so if there's going to be any changes in the pH, I'd prefer to do it before I get them. Really, before I get anything new fish. We moved the tank here two weeks ago, keeping maybe 1/2 the original water. I siphoned it out a couple times the first week, since I don't think that had been done in over a year, and my gosh, the poop! So, I know pretty well what the water is that went INTO the tank.
And thanks everyone for the input!
 
If the tap water is pressureized there maybe some CO2 bubbles in the water===Lower PH.

Your water seems very soft===Unstable PH

Looks like lots of plants, which pulls CO2 from water=== Higher PH
 
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