Does this feel right for CO2 ramp-up?

[Bradders]

Right, ladies and gentlemen ......... back to me understanding the science with your help. (Thank you, by the way).

• 24-hour degassed tank water by leaving in a cup to stand, pH7.7 (almost spot on my tap water readings, and would make sense).
• Tank water when CO2 is off seems to settle/buffer at ~ph7 (Is this the aqua soil?)
• The current tank pH with CO2 on is pH6.37 and steady.
• The CO2 Drop-Checkers (I have two of them) are lime green. 4 Green Neon Rasboars are acting normally, some pearling going on. (Pic below).

So here is where my little brain is getting confused.

1. Based on the degassed level of pH 7.7, I am well over-injecting CO2 into my aquarium.
2. Based on the tank water (when no CO2 is on and good aeration) at pH 7, I have not hit the full 1 pH drop.
3. My drop-checker is green, and pearling is going on. (You can confirm in the picture).

Is anyone willing to un-confuse me and explain in terms that a 10-year-old can understand? 😀

 

[Maf 2500]

My take is you are getting a pH drop of 1.33 at 6.37 which equates to 40-ish ppm CO2.

It might be that the level of 7 it typically gets to in the morning is because it has not had enough time to fully outgas the CO2 before it turns on again. (Also remember that plants are adding CO2 in the night, not consuming it.) What colour is the drop checker in the morning before the CO2 turns on? If the CO2 is fully outgassed it will be blue.

What sort of aqua soil is it? Any potential buffering will depend on this.

 

[Bradders]

What sort of aqua soil is it? Any potential buffering will depend on this.

Its Tropica Aquasoil. Which states it lowers the PH. And it does seem to do that. (Tap at 77, seems to settle around 7)

My take is you are getting a pH drop of 1.33 at 6.37 which equates to 40-ish ppm CO2.

Yes, if taking the water before the buffering of the Aquasoil?

What colour is the drop checker in the morning before the CO2 turns on? If the CO2 is fully outgassed it will be blue.

I am going to double-check this tomorrow, take a photo and post here.

 

[Maf 2500]

Hmm, I am not sure how buffered water reacts when it is removed from contact with the aquasoil...

You could try leaving a jug of water out for 24 hours, as before, but add a small handful of aquasoil substrate from the tank and see what value it stabilises at?

Or the nuclear option - leave the CO2 off one day and see if the pH in the tank rises above 7? Not really recommended but would provide some data.

 

[hax47]

• 24-hour degassed tank water by leaving in a cup to stand, pH7.7 (almost spot on my tap water readings, and would make sense).

The water from the tap contains CO2. Some tap water contains more, some less. Your degassed tank water also contains some CO2, depending on the time you left it on air, and also on many other things, like the amount of water in your cup, the surface of it, the CO2 in your room... So, whether the pH is the same in this sample, or different than in tap water, it really doesn't tell anything.

• Tank water when CO2 is off seems to settle/buffer at ~ph7 (Is this the aqua soil?)

When the CO2 is off, the concentration starts to drop at a rate dependent on surface agitation, actual CO2 concentration in the water and your room, surface area, etc. Also, you have constant CO2 production in the aquarium, so you can't expect to have degassed water in the tank even after having CO2 off for a while. More CO2 --> lower pH. It is not the aqua soil, it is the higher CO2 concentration that makes the pH lower.

The 1 pH drop method is based on the assumption that the fully degassed water contains exactly 3 ppm of CO2. However, this is probably rarely the case. Fully degassed water with 3 ppm CO2 would mean around 1800 ppm CO2 in your room, which is a bit too high to be accepted as a general value. Degassing needs time, and people probably don't wait until full degassing, which most likely leaves them with water above the equilibrium CO2 levels, hence the 3 ppm might be a good value after all.

Having 7.7 pH in degassed water means that you have some CO2 in your room and you reached some level of equilibration, but this might not be exactly at 3 ppm. If it was for example 1 ppm after equilibrium, you would need about 1.5 pH drop to reach 30 ppm. If it was 2 ppm, you would need a drop of ~1.2.

The method of aiming for the pH drop would be more accurate if the water sample were exposed to atmospheric air (outdoors), strongly aerated with an air pump, and aiming for a 1.7 pH drop compared to that measured level. The external CO2 level is more stable than the indoor CO2.

Based on the degassed pH level of 7.7, I am well over-injecting CO2 into my aquarium.

Maybe you are, or you are not. That depends on how well you have degassed the water and what is your room CO2.

[*]Based on the tank water (when no CO2 is on and good aeration) at pH 7, I have not hit the full 1 pH drop.

We don't know at what level is your CO2 at a pH of 7, meaning that you may or may not need the full 1 pH drop.

[*]My drop-checker is green, and pearling is going on. (You can confirm in the picture).

This is the most important. If the drop checker is green, you are probably somewhere around the good CO2 levels.

 

[Bradders]

OK, thank you, everyone. I think I have probably wasted a lot of people's time explaining this! But I am grateful for helping me understand the science a little better.

And of course, I'll always be ensuring that dop-checker is green, good gas-exchange and will watch the health of livestock.

 

[Zeus.]

Right, ladies and gentlemen ......... back to me understanding the science with your help. (Thank you, by the way).

• 24-hour degassed tank water by leaving in a cup to stand, pH7.7 (almost spot on my tap water readings, and would make sense).
• Tank water when CO2 is off seems to settle/buffer at ~ph7 (Is this the aqua soil?)
• The current tank pH with CO2 on is pH6.37 and steady.
• The CO2 Drop-Checkers (I have two of them) are lime green. 4 Green Neon Rasboars are acting normally, some pearling going on. (Pic below).

So here is where my little brain is getting confused.

1. Based on the degassed level of pH 7.7, I am well over-injecting CO2 into my aquarium.
2. Based on the tank water (when no CO2 is on and good aeration) at pH 7, I have not hit the full 1 pH drop.
3. My drop-checker is green, and pearling is going on. (You can confirm in the picture).

Is anyone willing to un-confuse me and explain in terms that a 10-year-old can understand? 😀

View attachment 223520

Nice colour change which indicates that you have about 30ppm CO2, your pH readings indicate you have a more than a 1.0pH drop which conflicts with the DC.
I would put the larger than 1.0pH drop down to the probe not reading the pH accurately. pH probes read the pH by proxy and the logarithmic scale of pH compounds the issue so the reading of the actual pH is tricky and prone to errors.
If you had buffering solutions of 7.0pH and 6.0pH and checked the solutions with the probe it would help demonstrate the limitation's of pH probes esp when it comes to accuracy of the pH readings over a range of pH.
I dont calibrate my probes any more. I use the DC for level of CO2 and the probe I used to see if how much drift/change in pH there is during the period from lights on till CO2 off. All we are after is a stable pH for the first 4 to 5 hours of photoperiod, knowing the actual pH of the water is irrelevant IMO

 

[dw1305]

Hi all,

This is the most important. If the drop checker is green,

That is it, it cuts through all the <"unknown unknowns"> whlch @hax47 & @Zeus. have mentioned above. Only gases can cross the air gap and only dissolved CO2 effects the colour of the pH indicator in the drop checker. You only have three components, CO2, pH indicator and 4dKH solution, and none of them are electronic etc.

I think @Andy Pierce posted this initially <"Drop checker - Fireplace aquarium">.

cheers Darrel