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Steady [CO2]/pH

Zeus.

Fertz Meister
Joined
1 Oct 2016
Messages
4,813
Location
Yorkshire,UK
Hi all

Achieving a steady [CO2]/pH from lights on till lights off or 4-5hours into the photoperiod is tricky, but its a goal we all try to aim for OFC. I wont go into why we need this steady [CO2]/pH as Clive has covered the reasons for it it his excellent posts.

Recently upgraded my pH pen to a Hanna HI-98129 and have been doing pH profiles on both my tanks for couple of weekends and had an epiphany of how to get the steady [CO2]/pH whilst doing the pH profiles.

We play around with the BPS to get the target [CO2]/pH for lights on then the [CO2] creeps up slowly. We decrease the BPS then it takes longer to get the target [CO2]/pH :rolleyes:

So what I I have done is similar to what a pH controller does without measuring the the pH. When lights go on, the CO2 goes off for 2.5mintes then back on again for 12.5 minutes, then rinse repeat for the rest of the CO2 period. the end result is a steady [CO2]/pH for the CO2 period to within 0.03/4pH via the Hanna pH pen.

Still playing with it ATM and might also need to keep the CO2 on constant when the lights are on the higher intensity as I do have them increasing during the photoperiod which will increase the CO2 demand of the plants. But I don't have them that high ATM so not an issue.

Obviously its all dependant on the number of time slots you can have on your timer OFC. Not an issue here as using a PLC there is no limit in real terms. (Infact didnt use a timer as such, used latching relays and on delays in the PLC software which are activated when lights and CO2 are on)

Just thought I would share ;)

Zeus

Edit - one tank has CO2 reactors and the other has an in tank atomiser.
 
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As long as the CO2 amount available for the plants is constant this can work ( you can use the pH controler for that i guess). I would be afraid if this becomes "mainstream" we would start seeing CO2 related problems more again.
Constant bps is easier and probably will create less problems.
 
you can use the pH controler for that i guess

I have used a pH controller but found the pH fluctuated at least 0.1pH between co2 on/off so if BPS was high it was on on off all the time fluctuating, if the BPS was lower the time between on/off was extended and still fluctuating, plus the pH probe drift played a factor too, so not keen on pH controlers for getting steady pH/[CO2]

As long as the CO2 amount available for the plants is constant this can work

Well the pH stays steady all photoperiod so all seems good ATM. Think a few things are helping this in my tanks.
1. CO2 reactors have CO2 bubbles in them even when the CO2 goes off, which helps buffer the off period.
2. With tank with in tank atomiser it has a long CO2 hose well over 1m which holds more CO2 than a short hose, so CO2 still bubbling when CO2 goes off, decreases slightly but then the CO2 is soon back on again
3.Using a PLC can have as short or long as on/off periods as I like. So lots of little short breaks once lights are on prevents a slow increase in [CO2] may be tricky with a normal timer due to number of time slots.

Think also will come in handy as I increase the light intensity for short periods for my carpet I can have the CO2 constantly on as CO2 consumption will increase. I have noticed when I turn the lights up there has been a pH increase in the past which I didnt notice till too late and algea was present.
 
I have used a pH controller but found the pH fluctuated at least 0.1pH between co2 on/off so if BPS was high it was on on off all the time fluctuating, if the BPS was lower the time between on/off was extended and still fluctuating, plus the pH probe drift played a factor too, so not keen on pH controlers for getting steady pH/[CO2]

Than check if the controler is susceptible to electric interfearance.. :) They are volt meters and electromachnetic fields can interupt with this making the probe go bonkers.
Can result in eratic readings and or even a buzzing relay... My Milwaukee has this isue anything close to the probe that contains an electric coil such as a pump or even something simple you never think of a mobile phone in your pocket and the darn thing goes mad.

For the rest, problems with a ph controler all are refering to improper use of the device.. The main concern that all permanent ph probes have that is actualy absolutely non ph related is... The permannet probe is connected to the power grid and it grounds your tank water.. In case you have a power leak in form of a defective leaking pump or heater device there will be a constant powerflow through the water.. Tickling you fish bellow the fins etc. Maybe at a very minor power leak they will be laughing from this sensation, but at higher voltages leaking it can make them unhappy and even sick.

The Ph controllers with a seperate ground pin next to the probe are actualy the worst.. These are the most stable in reading because the have a 2 point reference and a steady flow with the ground pin.. But also need a higher working voltage by itself.. In have a Hana with using a 2 point reference and it sends 5 volts through the tank water. Also no good for the fish on the long term.. I found out myself, sticking a finger in the tank and touching the central heating and it started tickling.. E checked and it was the hanna ph probe.. :shifty:
 
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Than check if the controler is susceptible to electric interfearance..

Well think it is as I does get an instant pH increase of 0.1pH when the T5 tubes come on. But not using the pH controler during the photo period, only use it for a second CO2 injection to get to the target pH which its does in about 48mins. Then dont just it again to control the CO2 injection, all done via PLC
 
Placing the controler in line as far away from anything electrical does the job.. You need a T and a IP68 swivel. I belie ve standard pH probe is 12mm. one pound and you're done.. :)

Mine is no longer in use, but still in line..
DSCF1341.JPG
 
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Hi Karl,
There are a couple ways to skin the pH controller cat. You can also reduce the bubble rate so that it takes longer to reach the target pH so that the solenoid is almost always on. Combine this with a very tight Low/High range or simply set a very Low target pH so that the controller can never achieve it and so the injection rate will be constant.

I agree with Marcel that the signal in the wire is very weak and susceptible to EMI so absolutely should be placed as far away as possible from wires carrying power.

Doing it with timers, as you are, can be tedious and as the plants grow or as you prune, the CO2 uptake rate will vary, week to week, so you really have to pay attention and you may have to adjust the timers.

Also make sure to calibrate the probe/tester frequently. :crazy:

Cheers,
 
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