Thank you so much to all of you who frequently post here. I've learned so much from reading your questions and posted answers.
I'm unclear on one key detail: how quickly can you drop the pH in the tank (to achieve the required CO2 concentration) while still keeping the inhabitants safe?
Background:
My questions:
I'm unclear on one key detail: how quickly can you drop the pH in the tank (to achieve the required CO2 concentration) while still keeping the inhabitants safe?
Background:
- I've got a 130 gal. "high tech" planted tank (high lighting, CO2) with Ultum Nature Controsoil (buffers the water) and several large pieces of Malaysian driftwood.
- I run it with a 40 gal. sump in the stand so I can keep all of the equipment hidden from sight.
- The tap water in my area is basically liquid rock ... so instead I use RODI water that I remineralize to 4 dKH using Aquavitro Carbonate, and to 4 dGH using Aquavitro Mineralize and Seachem Discuss Trace
- The new water has a pH of around 7.8 to 7.9 before being added to the tank
- I use an Apex controller to monitor the pH of the water flowing through the sump, and cycle the CO2 solenoid to maintain the pH around 6.7 (see control chart from my Apex ... orange trace is pH, blue bars are when CO2 is on)
- I have Discuss in the tank, along with a few bushynose Plecos, Rainbow fish, Siamese Algae Eaters, Greman Blue Rams, and Tetras
- The tank is quite heavily planted with several slow-growing species of Anubias, Buce, and Amazon Swords
- In case it is relevant, the tank stays at 82 degrees F.
- I perform a 25% water change every 3 days (I am always worried about water quality for the Discus, and like seeing crystal-clear water).
- I fertilize using Aquavitro's line (envy, propel, activate, and synthesis), following the recommended dosing schedule
- According to the pH/KH/CO2 chart, I should have a CO2 concentration of around 38 ppm (which I assume is a safe estimate, since I am remineralizing RODI water with only carbonate hardness)
- However, my drop checker in the tank is very blue
- Given Tom's earlier reservations about only relying on pH and KH values to determine CO2 concentrations, I am assuming the drop checker is correct and that I should change the control band on the APEX to drive my pH lower and increase CO2.
- The Discus (and other tank inhabitants) should be OK as long as I keep pH above 6
- I have read that it is important to limit the fluctuation of pH to no more than 0.2 in 24 hours
- While I can slowly drop the pH to a new target (perhaps 6.2) over several days, I am concerned about how much the pH will fluctuate each time I perform a water change. The new re-mineralized water will still come in at a pH of around 7.8 (assuming I continue to adjust its Alkalinity)
- At the same time, I've read other posts here from folks who seem to have routine fluctuations of pH greater than 1 over the diurnal cycle (due to timing CO2 injection with the light cycle)
- I'm also worried about keeping the fish in water so close to a pH of 6
My questions:
- How much can pH swing in a relatively short period of time without distressing the fish?
- Depending on the above, when I perform a water change, should I introduce new water that has only been re-mineralized for GH (so there's not a swing in pH in the tank) and then slowly add buffer to the tank until I restore KH to my target?
- Outside of water changes, would it be better for the fish if I added more buffer to the water (Carbonate), instead of trying to keep the pH so low? (this stuff isn't cheap)
- Am I over-thinking all of this?