PH profile, good then bad?

[Nick potts]

Hi all.

So in the eternal struggle to get CO2 spot on a decided to invest in a PH monitor for the tank and do a PH profile.

Setup and calibrated it this morning and left it running on the tank noting the degassed PH which sits at around 6.

Gas came on and 45mins later the PH was 5.3 which I thought was pretty good. Came back an hour later and the PH was at 5.4 and has slowly risen the rest of the day, with a jump to 5.6 after lights had been on for a while. I have checked the ph using a second meter and a liquid test.

Drop checkers are a nice light green.

So what would cause this drop then to rise, is it the plants using up CO2? or something else?

Tank is a 60x30x18cm shallow
1200lph external filter returned via a lily pipe
300lph surface skimmer
CO2 at 3-4bps, aquario diffuser into the external intake.

TIA

 

[Gorillastomp]

This means your injection rate is a bit too slow for plants uptake.

It could be that the injection rate is too low or the loop where the co2 in injected is too slow.

you mention that you degassed water was ph 6, is the water tested right in the aquarium ? If yes i would recommend to take a dample out of the fishtank and shake it and let it sit for couple hours to make sure it degas competely. If this ph is still 6 then you have your real starting point.

 

[Zeus.]

This means your injection rate is a bit too slow for plants uptake.

Increase the injection rate till the pH is stable from 'lights on' till CO2 off. Difficult as the CO2 on time has yet to be found - so stable pH for a given injection rate/BPS. Once stable Do NOT Adjust the injection rate again) then time how long it takes from an overnight degas of the tank to reach your target pH, the time it takes is the time it takes, if you adjust the injection rate again you will mess up your stable pH.

With twin injection and twin solenoids and timers you can shorten the pre CO2 on time - But with a single injectors/solenoids/timer you can not, it is what it is

If yes i would recommend to take a dample out of the fishtank and shake it and let it sit for couple hours to make sure it degas competely

I prefer to leave it 24hrs - I leave a glass of tank water on top of tank or next to it

 

[ceg4048]

So what would cause this drop then to rise, is it the plants using up CO2?

Yes.

Cheers,

 

[Nick potts]

This means your injection rate is a bit too slow for plants uptake.

It could be that the injection rate is too low or the loop where the co2 in injected is too slow.

you mention that you degassed water was ph 6, is the water tested right in the aquarium ? If yes i would recommend to take a dample out of the fishtank and shake it and let it sit for couple hours to make sure it degas competely. If this ph is still 6 then you have your real starting point.

I really should have done this, totally slipped my mind, I will take a sample out and leave it 24 hrs

Increase the injection rate till the pH is stable from 'lights on' till CO2 off. Difficult as the CO2 on time has yet to be found - so stable pH for a given injection rate/BPS. Once stable Do NOT Adjust the injection rate again) then time how long it takes from an overnight degas of the tank to reach your target pH, the time it takes is the time it takes, if you adjust the injection rate again you will mess up your stable pH.

With twin injection and twin solenoids and timers you can shorten the pre CO2 on time - But with a single injectors/solenoids/timer you can not, it is what it is



I prefer to leave it 24hrs - I leave a glass of tank water on top of tank or next to it

I have reset the on time so it is now on 3 hours before lights.

I have no problem upping the co2, I did think I had a high rate considering the tank size at around 30 litres.

Yes.

Cheers,

👍

This CO2 malarkey is confusing lol, if I were just going off the 2 drop checkers i would think all is fine, but if the PH profile (after I test totally degassed water) is right I would be rather far off the ideal.

I may also change my injection method, I had better results using a powerhead to disperse the co2 and the bubbles in the tank don't bother me.

 

[ceg4048]

This CO2 malarkey is confusing lol, if I were just going off the 2 drop checkers i would think all is fine, but if the PH profile (after I test totally degassed water) is right I would be rather far off the ideal.

It doesn't even matter if you have 15 DCs. The distribution of any of the dissolved gases, if it could be visualized, It would look like a vector field, with a different value and a different rate of change of value at every point in the field. So there is no point in using multiple DCs. Simply use one at any location and use it as a proxy for the distribution within the 3 dimensional flow field. We see these kinds of representations when we watch the weatherman giving us the bad news about more rain or a coming draught, or a blizzard. Well that's what's happening inside the tank, not just for CO2, but all the gases as well as for the water's velocity, temperature and pressure. "...The DC is a guide Neo. It can show you the path..." but it cannot give you an instantaneous reading that is representative of all physical points in space within the tank.