Freshwater PH Question - tap water + agitation

[FiddlersReef]

Sorry for a non-reef question, but I haven't found a freshwater forum with anything close to the level of knowledge here, and I'm hoping someone can help me understand for a cichlid tank I'm setting up as a cousin to my reef tank.

My new tank is a Waterbox Marine DX 110.4, because if this doesn't work out, it will be another saltwater tank. ;-) I've read that I want a target PH of about 8-8.2, and that frequently tap water will hit that mark. Great, I'm thinking, less RO/DI water usage for this tank.

So I test the water straight from the tap using an API freshwater test kit (all I've got for FW, sorry) and it is off-the-charts high. Like vivid dark blue. According to the test chart, that's 8.8+

So I throw an airstone in it and let it sit for 3 hours, test again and it's 8.2. Ok, well that would be perfect.

Then I let it run overnight for grins, and test this morning and it's about 7.6!

So now I'm confused about how to proceed. I'm going to use aragonite "chichlid sand" in the tank, which is supposed to buffer the water to about 8.2, so maybe it's ok to just agitate water-change water for a few hours and it's good to go?

Or is it just going to continue to drop once the pumps are circulating and agitating the surface in the tank, making the trip to the sump, etc.

Or should I just use RO/DI and make my own by adding some sort of Rift Lake salt, etc.?

 

[Sharkbait19]

To my knowledge heavily oxygenated water is going to have a higher pH. You are going to want a buffer like crushed coral or aragonite to keep it high though.
Don’t worry, API is actually the gold standard for FW test kits - from what I’ve been told everything else tests to much higher precision than really necessary in freshwater.
What kind of cichlids? I’m assuming rift lake cichlids at this pH. If it stays at 7.6, that is okay for the Malawi cichlids.

 

[FiddlersReef]

What kind of cichlids? I’m assuming rift lake cichlids at this pH. If it stays at 7.6, that is okay for the Malawi cichlids.

Well, this is all new to me (not freshwater, but cichlids). I've always wanted to keep them but never took the time to set up the right tank. I'm planning on Peacocks (Aulonocaras), so that's native to Lake Malawi.

You're right, I see it does say 7.5-8.5. I was thinking it was higher.

I do have four bags of aragonite "cichlid sand", so hopefully that will take care of the PH going forward. So many years of reefing has me very afraid of tap water, so I have to get my head around the idea that it's ok to just add prime, stir, and go.

 

[Rmckoy]

I remember when I was a lot younger before my first reef my uncle had a 200 gal African cichlids setup
There was tons of water movement with a large return pump , sump , crushed coral for the bottom .
The structure inside was constructed mostly of dry rocks ( the same as we use in our reefs . And layers of flat slate like rocks .

there was never any issues with ph .

there used to be buffers to achieve higher ph and general hardness .

 

[Randy Holmes-Farley Verified Community Expert]

Just like in seawater, the oH of freshwater is determined by the carbonate alkalinity and the CO2 level.

Aquaria consume (day) and generate CO2 (night and possibly day) and aeration tends to drive the CO2 level toward home air, which may raise or lower CO2 and pH.