Water Unstable

[philak]

Seems my tap water is quite unstable. If left in an open container for two days (as a test i used one ceramic saucepan and one metal saucepan and both returned the same result) it goes from a PH of 7.4 to 8.2! Water left in a closed drinks bottle over the same period stayed at 7.4. I assume the former effect is due to gassing off of chlorine?

In the tank the PH is stable at 7.4 but shoots up to around 8.2 when i redose with ammonia for the fishless cycle and gradully settles back to 7.4ish as the amonia goes to 0 (over 24 hours curently). The substrate is a mix of eco complete over gravel and silica sand at the front. The tank is also planted and has bogwood.

I've read lots on here about PH crashing during cycling but never shooting up like this due to ammonia. I'm using the same ammonia that i used to cycle my girlfriends tank and i never saw this effect in hers.Nitites are over 5ppm currently as im going through the spike. I'm happy if the final result will be a PH of 7.4 but i'm wondering if it will go up again once fish are in there and creating waste.

Does all of the above mean a potential low KH? No test kit for that yet.

 

[OldMan47]

The ammonia that we use is in the form of ammonium hydroxide in a water solution. It is a weak base and will always raise the pH unless there are other buffers in the water to counteract it. Since most of us have harder water, we seldom actually see much of an effect on pH but it is still there. The open top container would reflect CO2 coming out of solution. CO2 is acidic and is quite common in pressurized water systems. In a modern water system, there is often chloramine rather than chlorine so it really does not gas off like chlorine used to do.

 

[philak]

Thanks for the info Oldman.

I bought a GH /KH API liquid test kit on the way home today.

My tank water is back at a PH of 7.4 with the ammonia back at 0 (time to redose) Nitrites are still v high.

Tank KH came in at 11 drops(197 ppm )and GH 19 drops (off the chart!! ) Both readings were similar for the tap water, so i guess i can truly say i have hard water.
This makes it even more surprising that i'm seeing the PH fluctuation as you said.

 

[OldMan47]

It does seem strange to see the pH swing that much in a hard water tank. The 19 drops is 19 german degrees of hardness BTW. Finally someone with water harder than mine. Your water is almost right for African rift lake cichlids or the common livebearers once you get the tank cycled.