Hinky pH

B

brookelyn

AC Members
Mar 18, 2004
183
0
0
46
Minneapolis, MN
Both of my betta tanks (a five gallon, and a three gallon) have had a pH of 6.8 for a month now. Originally, both tanks had 7.2 due to the R/O water I was using, but after awhile, I decided to switch on over (slowly) to regular tap water (which has a pH of 7.8). Even though the tap water was at 7.8 both my tanks would test 6.8 once the water was in the aquariums. I didn't quite understand why there was such a difference, but my bettas seemed happy so I didn't worry about. Better to have stable pH, after all than to try to monkey with it, and cause a unwanted crash.

Here is my problem, though. Last week (Saturday), I added Java Moss to both tanks. When I did my weekly 30% water changes on both tanks that Sunday, the pH was at 6.8. However, today when I tested the pH prior to making the usual 30% water change, it read 6.4 on my five gallon tank, and 7.2 on my three gallon. What would cause such a big change in both tanks over a period of one week? Could it have been the addition of Java Moss? If so, wouldn't both tanks have had same reading of either 7.2, or 6.4?

It should be noted that neither tank has any medications in it, but my three gallon is currently having a bit of a brown algae problem.
 
Tested some tap water I had sitting out overnight, and I got a reading of 7.6.

I don't have a testing kit for KH (master kit I have didn't include it), so I am not sure what the tap water, and tanks would be at. The GH of the tap (and tanks) is 107.4 if that helps any, though.
 
Last edited:
Not really. GH and KH are only loosely related. GH measures calcium and magnesium ions. KH measures the buffering strength of your water, that is, its ability to withstand changes in pH.

Buffers are compounds like carbonate (CO3--) and bicarbonate (HCO3-), these are the two most common in aquariums. Compounds like PO4 and tannins are also possible and can contribute to the buffering capacity.

The conversion of ammonia to nitrate (through nitrite) uses up your buffer, hence one of the many uses for water changes is to replenish your tanks' buffers. If you have "soft water" or rather, water with little buffering, then you need to change more water more often to prevent biology from changing your pH.

How did you measure 107.4? That seems too precise for any hobby kit. However, going on that, I would guess (complete shot in the dark without a proper test) that you have decent buffering strength.

Like I said, I'm just guessing, based on carbonates usually being associated with calciums and magnesiums. If you want to diagnose pH issues, knowing your KH (or alkalinity is key).
 
Thanks for the response.

I got the GH reading from my GH test kit, which was included in my liquid AP (Aquarium Pharmaceuticals) freshwater master kit. It took 6 drops to turn the water in the glass vial green, and according to their (AP's) chart that makes it 107.4.

I'll have to see about picking up a test for KH this weekend, and get back to you on what it says.
 
Okay, finally was able to locate a KH testing kit, and it would appear I have a KH between 0-50ppm (in my tanks). It took two drops to turn the water from blue to yellow. Not a lot of pH buffering here, which could be why I am having issues with the pH. However, from the tap, I have a KH of 50-100ppm (four drops)

Is there anything I can do to increase the KH in my tanks? Also why is there such a difference between the water in the tanks, and the tap water?
 
Last edited:
How often do you do water changes?

A couple things that can decrease the KH in your tank:
biogenic decalcification - some plants can use bicarbonate as a carbon source if there's insufficient CO2. It's not their prefered source, but they'll use it in a pinch.

nitrification - nitrifiers use bicarbonate as their carbon source (and ammonia or nitrite as nitrogen)

So if you're derelict in your water changes, then your tank's KH can decrease in time, resulting in a pH increase.
 
Happychem - didn't you mean that the ongoing decrease of KH will result in a decrease of the pH?

Actually the nitrification process itself generates acid, so burns up alkalinity. The biomass of the nitrifiers is not great, and although they are likely to use carbonate/bicarbonate as carbon source, that use would be smaller than the acid production's requirement for neutralization.
 
I do a weekly 30% water change.

As of yesterday, I started adding Flourish Excel to both tanks, as I was told it would help my java moss (and the java fern I hope to get this weekend) to grow, and stay healthy. Not sure if this will help the KH level at all, but I figured I'd mention it.
 
You must log in or register to reply here.
AquariaCentral.com
Top Bottom