Help solve my PH conundrum

[waterwookiee]

So, I've been setting up my 20h planted tank and most has been going great. Look for a journal soon. However PH has been a challenge. Here's they mystery.

My untreated well water has a GH of 1, KH of <1 and a PH of 6. This is even after it sits still, and airated for several days.

I first did my tank with Floramax Midnight and it was causing PH spikes off the chart. Took it out, scrubbed everything out and reset with Flourite and retested. PH 6, KH <1, GH 1 both right after the refill and everyday for four days. Problem solved.

It was a bit too soft, so I buffered with a smidge of baking soda. PH up to 7.6+, KH to 8, GH at 4. After numerous water changes, I've been able to get my KH down to 3 and stay stable, however my PH won't budge down below 7.6(+?). I change up to 75% of the water at a time, and it goes down for 6 hours or so, then starts to creep back up????

Did the Substrate absorb the bicarbonates?
Can my lighting be causing a reaction in the water chemestry?

Only other additions since then have been as follows.
One chunck of African wood (throughly boiled)
Two packs of whisper biomax bio media (ceramic)
Four glowlight tetras and a handful of plants.

And ideas??????

Thanks!

[waterwookiee]

I should add that since the plants arrived, I've done two tiny doses of Flourish complete.

[KH2PO4]

If bicarbonate gets absorbed, your KH will come down. So this is not the case here.

Are you injecting CO2? If not, then it's rather normal. The low pH you got just
after water change came from CO2 in the tap I think. At 3 dKH and pH of 7.6,
there is 2.65 PPM of CO2 which is very close to the equilibrium with the air.

[waterwookiee]

I've started a rather anemic flow of DIY CO2 (1 bubble every 2 seconds). That will be improved tonight. I'm hoping that brings it down a bit, but the worry is that KH of 3 isn't enough to keep greater amounts of CO2 from causing wild PH swings. However I'm also afraid that if I bring the buffering capacity up just a bit more to say 5 or so, I'll further spike the PH. I want to avoid torturing my soft water tetras. I know I want to leave it alone and not chase it, but my tap seems too acidic and soft for most applications. Thus my conundrum.....

[wkndracer]

The low GH will be a problem for the plants (imo)
Your 'smidge' of baking soda must have been a bit larger than a pinch LOL
Using RO I add about 1/2tsp for 1dKH in 26 gallons of water.
Yes the flourite will absorb some of the buffer from all that baking soda then leach back into softer water but it will exhaust over time.

[waterwookiee]

Yup, I ODed on baking soda, but that was pre-fish so no harm no foul. Whats a good target KH and GH? How can this be acheived without killing my tetras with high PH?

[wkndracer]

Avoiding source water problems I use 100% RO product water (2ppm TDS).

General hardness adding GLA's ultimate booster, any number of branded GH boosters will work I'm sure.

Carbonate buffer = A&H baking soda.
Leveled spoons
To increase KH
1/8 TSP : 6.4 gallons = 1dKH
1/4 TSP : 13 gallons = 1dKH
1/2 TSP : 26 gallons = 1dKH

CO2 injected or NPT low light I range the water hardness the same 2dKH, 5dGH.
pH will swing up daily almost a full degree/point during the photo period mainly based on CO2 content on my 'low tech' tanks. The fish and I ignore the pH monitor LOL
(they swim in the mineral content not the pH reading )

[waterwookiee]

I understood CO2s ability to make water acidic relating to the interaction with carbonates thus creating carbonic acid. In the case of my very soft well water, or RO water for that matter can CO2 make the water more acidic with little or nothing to react with? Is RO water automatically neutral PH? What happens to PH if you pump CO2 into pure (RO) water?

This is really interesting!

[wkndracer]

Pure water is neutral.
pH of 7.0 is considered neutral (mid scale).
Below a pH of 4 everything in the tank dies I believe.

The pH scale is logarithmic, each whole pH value/point is ten times more than the next lower or higher value. 4pH is ten times more acidic than 5pH and 100times (10 times 10) more than 6pH.

With 2dKH measured on tank water CO2 drives two of my tanks down to 5.8 and 5.95pH (controller setpoints) and keeps it there. Ashamed to say working 12hr shifts 7 days a week those tanks have gone up to 3 weeks without water change or mineral modification. Good news is everybody lived LOL.

Knowing a little water chemistry is a good thing

[waterwookiee]

As an experiment I mixed up a double dose of yeast, and took my "dark period" airstone out of the mix and just as predicted by the fine folks here, my PH was down to 6.6-6.4ish with a dKH of 3. I'm now feeding about 1 1/2 to 2 bps into the tank. Brilliant!

[waterwookiee]

Does the GLA ultimate booster affect the KH since it contains calcium? Also, I've started dosing Seachem Flourish Complete, wouldn't that boost the GH too (given that it contains calcium, magnesium etc.)?

[KH2PO4]

Originally Posted by waterwookiee

Does the GLA ultimate booster affect the KH since it contains calcium? Also, I've started dosing Seachem Flourish Complete, wouldn't that boost the GH too (given that it contains calcium, magnesium etc.)?

Nope they wouldn't. Calcium and Magnesium affect only GH
(hence the name of the product).

Stuffs ending with "HCO3" "CO3" will raise KH, such as
NaHCO3, K2CO3, KHCO3, CaCO3, MgCO3, etc.....

[waterwookiee]

Got it! Thanks again.