Optimising CO2 levels in a low pH and kH aquarium

Dear FishLore community,

What is the best way to determine I am injecting ~30ppm of CO2 into my planted tank?
A lot of websites advise that this amount of CO2 is the sweet spot for plant growth as well as prevention of algae.

I have soft tap water, with the tank having a low pH of 6.4 and kH of 2 prior to CO2 injection, with a relative drop to pH 5.9-6.0 after CO2 stops.
I suppose it is also exacerbated by having ADA soil which readily lowers pH from the tap (pH 7.2, kH 2).
I have seen the table (red/green/yellow) which utilises pH and kH to determine how much of a relative drop in pH I need to achieve optimal levels however, according to the table, I have 24ppm even before CO2 is on, and 60ppm with the drop in pH. I know this to be strange as I am battling a severe case of BBA and GSA, in which I attempted the one-two punch method (hydrogen peroxide + excel) but I digress.

Another website mentioned that CO2 levels were independent of kH, and that a better goal was to aI'm for a decrease in pH unit of 1.0-1.2 i.e. 6.4 to 5.4. I feel this is somewhat dangerous for my tank as when I approach 5.7, my bottom dwellers (corydoras) exhibit signs of gasping and abnormal behaviour of swimming nearby the powerhead/higher areas of the tank.

Should I attempt to raise my pH and kH through external means? I believe using marble chips could work, as I'd rather reach an equilibrium with them as opposed to constantly add baking soda.
I also think there is also the possibility of poor gaseous exchange as my tank sits at pH 6.4; would residual CO2 levels be the cause? I am thinking of either running an airstone overnight or purchasing a surface skimmer.

All in all, I was hoping if anyone had any advice or thoughts on my situation.

Help much appreciated, thank you.
Kim

 

Welcome to Fishlore hope our Co2 users can help you today

 

I can help out when I’m back to a computer. I’m short on time atm.

 

You will need a drop checker.
The pH/KH/CO2 table is flawed because it assume that the only acidifier in your tank is CO2 and the only buffer is the KH. That's clearly not your case. ADA soil leaks fulvic, humic and other organic acids and lots of nutrients(hence the algae) in the first few months.
I would not use marble chips to increase pH and KH because it will dissolve excessively in an acidic environment and the GH will go up a lot. It will also work against the soil.
Given your soft/acid tap water (I wish I have that...), I'd stick with fish that thrive in such an environment and avoid livebearers.

 

5.4 is fine for most fish, pH drop from CO2 of 1.0 = roughly 30ppm of CO2 in the water.

Gasping fish = too much CO2.

Do not add anything to adjust your kH or pH, your soil is doing it's job dropping the pH of the tank.

I would get a drop checker, and you'll want it to be a light green, almost yellow colour for the max safe amount, and consider running an airstone at night only, at higher CO2 levels. Keep a decent amount of surface agitation from your filter to allow good gas exchange.

A full green drop checker is not yet at the limit of the tank. Work up CO2 levels slowly over a few weeks so allow fish to adjust.

You might be able to get away with going on pH drop if you've exhausted the soils buffering abilities. Your pH and kH reading aren't adding up... a tank with a kH of 2 should have a pH 7.2-7.4 ish, leading me to believe the kH is 0 like it's supposed to be, resulting in your pH of 6.4 (exactly where ADA soil levels out).

 

You will need a drop checker. The pH/KH/CO2 table is flawed because it assume that the only acidifier in your tank is CO2 and the only buffer is the KH. That's clearly not your case. ADA soil leaks fulvic, humic and other organic acids and lots of nutrients(hence the algae) in the first few months.

Thank you, I will hold off on the marble chips. I was confused regarding that table as my drop checker showed blue when CO2 was offline, yet theoretically according to the table, I would have 24ppm, even though 0ppm had been provided to the tank. It was perplexing as many articles/individuals were advocating for the table and scrutinizing the drop checker's accuracy.

5.4 is fine for most fish, pH drop from CO2 of 1.0 = roughly 30ppm of CO2 in the water.
Gasping fish = too much CO2.

I would get a drop checker, and you'll want it to be a light green, almost yellow colour for the max safe amount, and consider running an airstone at night only, at higher CO2 levels. Keep a decent amount of surface agitation from your filter to allow good gas exchange.

Thanks, I will slowly work my way to 5.4 over the coming weeks. I will disregard the kh/ph table as it scared me into believing that at such a pH, my CO2 levels would be through the roof. I'll also position my outflow so it'll increase surface agitation, although I believe that would lead to some dead spots in the tank. I might have to add a weak wavemaker or powerhead.

 

Thanks, I will slowly work my way to 5.4 over the coming weeks. I will disregard the kh/ph table as it scared me into believing that at such a pH, my CO2 levels would be through the roof. I'll also position my outflow so it'll increase surface agitation, although I believe that would lead to some dead spots in the tank. I might have to add a weak wavemaker or powerhead.

Adjust CO2 slowly (over a few days) and try not to leave the tank unattended for too long just to be on the safe side.

You can buy a universal intake skimmer for the canister filter to increase surface agitation and not harm your current flow pattern.

 

Adjust CO2 slowly (over a few days) and try not to leave the tank unattended for too long just to be on the safe side.

At which point is it a good time to reach 30ppm? I've read others injecting 2 hours before and turning them off 1 hour before lights off. Is it possible to achieve 30ppm when lights start? If that is the case, theoretically, would it mean having a constant balance between 30ppm in and an x amount of off-gassing (via a skimmer)?

I believe I am achieving a lime-green colour with the drop checker towards the end of my light period with significant plant pearling so some CO2 adjustments are in order.

 

At which point is it a good time to reach 30ppm? I've read others injecting 2 hours before and turning them off 1 hour before lights off. Is it possible to achieve 30ppm when lights start? If that is the case, theoretically, would it mean having a constant balance between 30ppm in and an x amount of off-gassing (via a skimmer)?

I believe I am achieving a lime-green colour with the drop checker towards the end of my light period with significant plant pearling so some CO2 adjustments are in order.

Within an hour or so of lights being on would be best. Plants grow best with consistent CO2 levels... so theoretically having CO2 at the same ppm throughout the entire photoperiod would be best.

Anyway, lime green towards the end would mean levels would only be reaching sufficient levels midway through the photoperiod, not ideal, so yes some adjustments are required.

2 hours before is probably a safe bet, I ran mine right until the end of the photoperiod, this way the ppm stays the same right until the end, at which point CO2 shuts off with the lights, so it can't continue to build up.

Running an airstone at night also helps with left over CO2 if need be.