My pH profiling experience

[erwin123]

Just sharing my recent experience with CO2 tuning. Its really hard!

I have a 60cm tank with about 80-90 litres of water (i.e. excluding the substrate) and I'm running a Qanvee inline diffuser and Neo Aquario in-tank diffuser and for almost a week, I was trying to tune CO2 and was unable to achieve a stable 1.2-1.3 pH drop as the pH would overshoot towards 1.4. My pH meter is an Apera PH60

And all I did was to increase my Qanvee diffuser CO2 from 1.5bps to 2.0bps and turning on CO2 3 hours before lights on. After a few days of failure, BBA started appearing probably due to CO2 instability so I gave up and went back to 1.5bps but left the CO2 to turn on 3 hours beforehand. I did a pH profile again and was satisfied with the result though I would have preferred a -1.2pH drop at peak CO2 usage, instead of -1.16pH

0.5bps (which translates to 20% more CO2) was the difference between pH crashing and stability. At 1.5bps, I managed a 'flat' pH curve for a few hours which suggests CO2 injection roughly equals CO2 consumption. Priority now is to fix the BBA which thankfully is only on two plants - the Cinerum's flower stalks and Hygrophila 'Lancea' and to rethink whether I can increase CO2 availability during the peak usage period.

As for easy improvements, I should turn off the Qanvee diffuser CO2 later than 2130. [I leave the Neo diffuser on till 2215] While some stems may be starting to close up, the fact that pH is rising suggests that some plants are still using CO2 even though I am slowly ramping down the lighting.

 

[jaypeecee]

Hi @erwin123

I was trying to tune CO2 and was unable to achieve a stable 1.2-1.3 pH drop as the pH would overshoot towards 1.4.

May I ask why you are aiming for a 1.2 to 1.3 pH drop? A quick calculation tells me that this would correspond to a [CO2] increase by a factor of 15.8 to 20.0. So, if the [CO2] starting point was, say, 3 ppm, the end [CO2] would be somewhere between 47 ppm and 60 ppm. That's awfully high if you have livestock in your tank but perhaps it's a plant only tank?

JPC

 

[erwin123]

I'm aiming for 1.2-1.3 to see if the plants grow 'better'. Anyway, currently I'm only at 1.16 drop at peak CO2 consumption - if I can nudge that to 1.2 that would be go enough to have results - the 1.3 is more like the max limit or warning level for me.

Reading up on what other aquarists who measure pH are doing, it appears that 1.3 is the highest they go with livestock (without livestock I guess anything goes). So I would like to try and and at the same time 'watch the shrimp', 'watch the fish' and
'watch the plants' to learn what effect it has. So far, if the baby cherry shrimp are acting normally, I would say 1.3 is not a problem for livestock (as confirmed by other aquarists who are doing 1.3 and if I search UKAPS I can see others who have gone up to a 1.4 drop.).

I had a CO2 regulator accident during filter cleaning (knocking the regulator while doing filter cleaning) and gassed my shrimp /fish maybe for a hour+. Fortunately, all the shrimp/fish that remained in the tank made a full recovery (I was not fishing out the bodies of dead baby shrimp for example). 2 fish jumped out so those were the unfortunate fatalities. But at least the learning experience is that I know what CO2 stress looks like.

As for those that do not measure pH, there are plenty of examples of journals where the user is like doing 3-4 bps of CO2 into a nano tank and the tank is filled with CO2 mist and yellow/greenish-yellow drop checkings. I'm only doing 1.5bps into a bigger tank and my tanks mist is not really noticeable compared to those journal photos I've seen, so I suspect that their tanks also have massive pH drops. So where CO2 is concerned, I think the 1.0 drop rule is more often honoured in its breach. Accepted that bubbles per second may not be an accurate guide... but looking at the tank full of mist, I'm sure they're injecting more CO2 than I am? 😅

Finally, my tank temp is 26 degrees so CO2 solubility would be less than a tank running at say 24 degrees. And given that my room temperature water for measuring degassed water pH is quite high, (i.e. CO2 solubility is less?), I'm also not 100% sure whether degassed water CO2 concentration would be 2ppm or 3ppm for my water (1.0pH drop is on the assumption of 3ppm CO2 in degassed water)

 

[Ria95]

Thanks for sharing the results. Indeed CO2 is the hardest to set from all the parameters because there are so many moving parts to it. Water level variation from evaporation can also mean slower or faster degassing rates which throws a wrench into many finely tuned tanks.

 

[erwin123]

Results of today's profile.
I set the in tank Neo Diffuser to turn on 30minutes earlier, and increased it from about 0.75bps to about 1.25bps.
The main Qanvee in-line diffuser remained at 1.5bps

This was the slightly odd result where pH started off high and then dropped to a rock solid 6.26. I measured 5 times in that period and get readings of 6.27/6.26. While variance appears higher at 0.15, this is actually pretty stable - if only it were slightly lower on lights on. Water in my tank is a 'warm' 26 degrees which could affect solubility limits.

Tomorrow is WC change which might change the pH of my tank water so I won't be able to do an 'apples to apples' comparison.

 

[Courtneybst]

I just noticed your post and realised we have almost identical problems! I'll be following to see if you reach resolution.

 

[Ghettofarmulous]

I set the in tank Neo Diffuser to turn on 30minutes earlier, and increased it from about 0.75bps to about 1.25bps.

I’d be careful about changing more than one variable at a time. Attributing a change to either variable would ge difficult and you may need a few more days to prove which variable enacted a change.

 

[jaypeecee]

Reading up on what other aquarists who measure pH are doing, it appears that 1.3 is the highest they go with livestock (without livestock I guess anything goes). So I would like to try and and at the same time 'watch the shrimp', 'watch the fish' and
'watch the plants' to learn what effect it has.

Hi @erwin123

Carbon dioxide has been demonstrated to be toxic to fish under some conditions. Please take a look at the following:

http://www.bioflux.com.ro/docs/2016.574-579.pdf

From the above paper, this is an extract:

"Bruno (1996) presented that there are two circumstances which are considered to cause or exacerbate nephrocalcinosis. Firstly, a prolonged exposure of fish to high levels of carbon dioxide at levels greater than 10 to 20 mg/L, and secondly a nutritional aspect where a magnesium deficiency and a selenium toxicity have been implicated."

JPC

 

[Zeus.]

Like @jaypeecee suggest your [CO2] is getting high, I have used high [CO2] before and you need to be careful even feeding the fish can send them belly up in the water.
What colour does your DC change? as a DC colour change IMO is the only true indication of [CO2] of the water in our tanks
Is the water surface 'scum free'
The pH profile does seem to behaving oddly! what filter and addition powerheads or skimmers are you using ?
you are using twin injectors but only one solenoid I take? so both come on together and off together, which CO2 slitter/twin needle valves are you using as some can be doggy to say the least
A full tank shot gives lots of other info also

 

[jaypeecee]

I'm aiming for 1.2-1.3 to see if the plants grow 'better'.

Hi @erwin123

It's just dawned on me that if the above is your objective for doing this experiment, then why have livestock in your tank?

JPC

 

[erwin123]

Like I mentioned, my degassed CO2 is measured by leaving a cup of tank water outside for 24 hours where it gets really warm (up to 30 degrees). If degassed CO2 content of this water is 2ppm and not 3ppm, then:

CO2 concentration - degassed water - assuming 2ppm
1.0 pH drop - 20ppm CO2
1.1 pH drop - 25.2ppm CO2
1.2 pH drop - 31.7ppm CO2
1.3 pH drop - 39.9 ppm CO2

I also looked at the amount of CO2 I'm injecting - the main CO2 diffuser, the Qanvee is only getting 1.5bps. The in tank one just sprays a bit of mist around the Rotala Floridas but is otherwise wasted (I've tested turning off the in tank Qanvee early and leaving the Neo on, the pH will start climbing quickly). So if I look at 1.5 bubbles per second into a Qanvee, and compare it with other aquarists who are doing a lot more bubbles a second, I wondering whether 1.5 bubbles a second is really enough to reach 60ppm CO2 (which would be the case with 3ppm degassed CO2) in 80-90 litres of water, with a skimmer active 24/7, or whether I am only injected 31-39ppm CO2 - which would be the case if degassed CO2 is 2ppm.

So I guess I should look at the livestock to see if there are signs of distress. The baby shrimp are fine, the shrimp are breeding.

(edit: I'll post a photo of the drop checker colour later today as additional 'data')

 

[erwin123]

CO2 has been on for 8.5 hours when this video was taken. Fresh drop checker solution used (blue before placing into the tank)
Drop checker remains green at 1.3pH drop, Shrimp and fish in video seem 'normal'

1.3pH drop assuming my degassed water contains 2ppm CO2 translates to 39.9ppm CO2- that might well be the case here?

 

[erwin123]

My final pH profile. I had to start my in-tank diffuser 30minute earlier to ensure that the curve flattens earlier. Total pH variance from lights on to CO2 off is 0.03. Drop checker is green throughout.

 

[JacksonL]

Looks like a pretty perfect profile to me

 

[erwin123]

thanks. the acid test (haha) will be whether I get any new BBA!

So far so good, I just have the old BBA to get rid of 😅

 

[arcturus]

I'm aiming for 1.2-1.3 to see if the plants grow 'better'. Anyway, currently I'm only at 1.16 drop at peak CO2 consumption - if I can nudge that to 1.2 that would be go enough to have results - the 1.3 is more like the max limit or warning level for me.

Reading up on what other aquarists who measure pH are doing, it appears that 1.3 is the highest they go with livestock (without livestock I guess anything goes). So I would like to try and and at the same time 'watch the shrimp', 'watch the fish' and
'watch the plants' to learn what effect it has. So far, if the baby cherry shrimp are acting normally, I would say 1.3 is not a problem for livestock (as confirmed by other aquarists who are doing 1.3 and if I search UKAPS I can see others who have gone up to a 1.4 drop.) (...)

I apologize, but I am going to be quite blunt here. It is fine experimenting how plants react to increased levels of CO2. But it is not fine performing that experiment with any type of livestock in the tank. Even if livestock seems to be acting "normally" (from your subjective perspective) that does not mean it is not being negatively affected by CO2 toxicity and/or oxygen deprivation, which can cause long-term inner organ and neurological damage. Once you start observing behavioural issues in the livestock you will be already way past the toxicity threshold. Moreover, you cannot say that a 1.2 or 1.3 drop is "not a problem for livestock" based on a few random internet forum posts. Let's not forget that behind all the fancy high-tech equipment we are responsible for taking care of the living creatures inside the tank.

 

[erwin123]

I apologize, but I am going to be quite blunt here. It is fine experimenting how plants react to increased levels of CO2. But it is not fine performing that experiment with any type of livestock in the tank. Even if livestock seems to be acting "normally" (from your subjective perspective) that does not mean it is not being negatively affected by CO2 toxicity and/or oxygen deprivation, which can cause long-term inner organ and neurological damage. Once you start observing behavioural issues in the livestock you will be already way past the toxicity threshold. Moreover, you cannot say that a 1.2 or 1.3 drop is "not a problem for livestock" based on a few random internet forum posts. Let's not forget that behind all the fancy high-tech equipment we are responsible for taking care of the living creatures inside the tank.

(1) My drop checker is green (video above - with livestock shown - looks normal to me). It has never gone yellow. Video was taken after CO2 has been on for 8.5 hours.
(2) 1.3pH drop is equal to 39ppm CO2 if degassed water contains 2ppm CO2.