Bicarbonate Based Ph Buffers

[amcalab]

Here is another strange thing about my tap water...When it comes out of the tap, its hard, but its alkalinity is low (3 KH) and its PH is through the roof.

Then after several days the KH appears to go up to around 5 KH and the PH comes down to around 7.2. I'm worried about water changes making the PH shoot up and then come back down -- PH Rollercoaster. But, I don't have the space to store and condition water for days. I need to be able to use water directly from the tap.

I have a bicarbonate based PH buffer (no phosphates). Are these really as bad as you guys make them sound?

 

[Liam]

It does sound strange to me. I don’t understand, test a sample of tap water after leaving it out for 24 hours, test kh gh and ph, then test for the same in your tank and see what the difference is, you can also test it straight out of the tap, that should give you a good picture of what’s happening. If you have a kh of three which is low its still enough to keep your ph stable. I wouldn’t use ph buffer myself if you are worried about the change in the water smaller more frequent water changes will solve the problem. Ph shock for fish is more about their inability to deal with changes in the amount of total dissolved solids in the water, ph is sort of a measure of this, this usually doesn’t vary that much in water supplies, depends on rainfall etc but the variation shouldn’t be too much of a problem. The ph of the water should go up when its left out as the Co2 comes out and there is less carbonic acid in the water. I would expect with a kh of three that you would have a ph close to 7, which is fine for lots of fish. Have you got strip tests or drop tests, the drop tests are more accurate. Sorry if that sounds confused.

 

[amcalab]

My PH starts off high (>8) but after 4 or 5 days it reads closer to 7.2.

So are you saying the PH drop is actually OK for the fish? And it is actually the changes in KH that we don't want?

 

[Liam]

Yeah that amount of ph drop is fine after 4 or 5 days, planted tanks add Co2 the ph can drop a full point without any problem. If your ph remains stable after the drop at 7.2 there is nothing to worry about. Yeah abrupt changes in the total disolved solids or GH are more the problem. its about the fishes osmoregulation, the balance between the fluids in the fish and in the water. A KH of 3 is low as I said but its enough to buffer the water against ph crash where the water gets suddenly acidic due to build up of acids in the water caused by the nitrogen cycle etc.