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c02, inline diffuser, ph meter readings....

Ady34

Ady34

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UKAPS Team
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Hi,
ive recently purchased a ph meter: HM DIGITAL PH-80 Handheld PH Meter: Amazon.co.uk: Kitchen & Home
I want to see what is happening with my c02 pre, during and post photoperiod/injection period, and after water changes etc. I feel this will be more accurate than a drop checker in a heavily misted tank. However my question is, when using an inline diffuser creating mist within the water column, does the actual mist of gas effect the ph reading of the meter directly (like it can in a dc) or does it only measure the ph drop from dissolved gas? Would it be best to remove a small sample for a few seconds until the mist has disappeared then take a reading of ph more inline with dissolved c02?
I understand the mist is there to directly feed the plants, but id like to know what the ph meter is actually reading.

Early readings show an overall drop in ph from 6.9 to 6.1, however these are not conclusive yet as i need to take more detailed readings post, pre and during injection.

Thanks,
Ady.
 
You could take a little water out of the tank, the CO2 bubbles will be out in a few seconds and than measure pH to see whether they really influence the meter.

I guess they will. If the CO2 bubbles come in contact with the electrode, you would get a lower reading than the pH from the water because of the local higher concentration of CO2. But I think this would be no problem, because your plants see the same amount of pure CO2 (the bubbles) so basically you measure what plants are seeing.
 
Hi ady ph meter measures the conductivity of the water so i dont think the mist will affect its readings. Im sure ceg or darrel will correct if im wrong. Ive just got a glass diffuser and with a 0.8 ph drop fish start showing signs of stress. I dont have a dc because of the delayed reading and i already have a ph pen
I feel that a ph profile taken with the pen is better than a drop checker and a dc is more expense i cant afford at the moment
 
mmm, im hoping it is measuring water ph irrelevant of direct gas contact because that would be the best of both worlds in a mist tank, good levels of dissolved gas along with a good mist for direct access.
Reading these posts from Clive in Deanos Journal, it suggests a 1ph drop to be sure of good levels, which is often not possible with livestock, so somewhere near isnt bad....just need to hope the lighting and distribution is suited then :rolleyes:
ceg4048 said:
The goal is to change the pH from the "pre-gas on" value to some value approaching a -1 unit pH difference. This is not always achievable without annihilating the fish. It's a very tricky business, but at lights on is THE most critical time of the day for CO2. That will make or break your tank. After about 4 or 5 hours of gas the plants really do not care so much about CO2. So it's possible to increase the injection rate and then to turn the gas off very early to avoid toxicity. When you turn the gas off early after a high injection rate, the residual CO2 content will feed the plants until the end of the photoperiod. Also, flow and distribution are primary factors, so if you want to avoid toxicity then you have to make sure that you have good flow rate and distribution techniques. That way you don't have to drive the pH so low because the flow and distribution will carry the CO2 more efficiently to the leaves.
Click to expand...

ceg4048 said:
Again, depending on the alkalinity of your water, it may not be necessary to drop the pH that low. If you measure KH to be much above 10 for example, then you may only need to drop the pH to around 5. High alkalinity kidnaps the H+ ions, so it masks how much acid is being produced, and therefore masks how much CO2 is actually being dissolved. That's why the dropchecker uses an acid free distilled water adjusted to a known low KH of 4, so that the color changes are predictable and consistent.
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My water is currently of low alkalinity so im looking at the higher end near a 1ph drop. Just need to ensure its there for lights on.

Thanks for the replies, ill hope for a definite confirmation either way....
 
I used a pH test to see what my co2 was doing, I bought an api liquid test and so far I only used it over 2 days and haven't used it again since I fine tuned my co2. I did hourly tests during co2 on time and it proved quite useful in terms of seeing how fast the co2 dissolves in the water and when the level is right for lights on and also when the co2 level begins to creep too high. I too was inspired by that very post by ceg4048
 
jacaranda said:
I used a pH test to see what my co2 was doing, I bought an api liquid test and so far I only used it over 2 days and haven't used it again since I fine tuned my co2. I did hourly tests during co2 on time and it proved quite useful in terms of seeing how fast the co2 dissolves in the water and when the level is right for lights on and also when the co2 level begins to creep too high. I too was inspired by that very post by ceg4048
Click to expand...
Yes it will be a useful tool in determining injection periods, rates and even gas off times to allow a better understanding of when to switch on and off. I'm interested to see how long the co2 hangs around in the water once injection stops.....but that will require a very late night possibly :)
 
Ady34 said:
Yes it will be a useful tool in determining injection periods, rates and even gas off times to allow a better understanding of when to switch on and off. I'm interested to see how long the co2 hangs around in the water once injection stops.....but that will require a very late night possibly :)
Click to expand...

Going on my readings which are co2 on at 2pm and off at 8pm (lights on at 3pm and off at 10pm) my pH readings start at 6.8 the drop to 6.2 by 8pm - it really depends on how much plant mass you have in the tank that will use up the co2 injected in - on mine at say 8am the following morning my pH reads around 6.5/6.6 as co2 has been used and driven off.
 
Gary Nelson said:
Going on my readings which are co2 on at 2pm and off at 8pm (lights on at 3pm and off at 10pm) my pH readings start at 6.8 the drop to 6.2 by 8pm - it really depends on how much plant mass you have in the tank that will use up the co2 injected in - on mine at say 8am the following morning my pH reads around 6.5/6.6 as co2 has been used and driven off.
Click to expand...

I think from what Clive suggests from the posts above, how far it needs to drop to have a good c02 level can depend upon alkilinity and maybe your tank is working well with less of a drop for lights on because the water is higher in kh and masking the extent of the fall/injection? With mine being low alkilinity ill have to ensure a bigger drop to get good levels.
The results i took yesterday levelled at ph 6.1, so im hoping to just tweak the c02 start time to get it there for lights on and then dial back injection rate slightly if i need to for fish. I do have some snails and very small crshrimplets in there now which are fine, although the shrimplets do start to swim around the water column more at about 9pm, (c02 shuts down at 10pm) dont know if thats irritation due to the level of c02 or just a thing they do, but if the shrimplets are ok, im guessing im about right for livestock :)
I think your morning results show slightly less of a rise than that just before injection (ph 6.8) due to the fact that plants also produce c02 at night so the rate of drop off will be slightly lessened as c02 is effectively still being introduced naturally via the plants? (unsure as to what level of c02 introduction plants add overnight so that maybe total balderdash :p )
If this is the case in my tank too i can expect a ph of maybe 7 before injection begins which will mean im nearly at a -1ph fall during injection :D .....ill find out over the weekend.
One thing i already know is that at my current rate of injection i need to start it a little earlier to get peak c02 for lights on, it was still at 6.2 1hr into the photoperiod yesterday, that was the first reading i took.

Cheerio,
Ady.
 
Big clown said:
If you start adding gas a hour earlier watch your shrimplets, if they start swimming round the water coloum a hour earlier then you know its co2 related. You can always stop gas earlier to keep livestock comfortable if this is the case
Click to expand...
Yep, true dat :)
That will be the beauty of ph readings. Ill be able to assess off gassing rates to determine how early I can switch off the gas :)
 
Mine gasses off pretty slow, at co2 off 7pm the pH is about 6.6/6.5 and at lights off 11pm the pH is 6.8.
The next day at co2 on time the pH is 7.2 and the base line test I did (left aquarium water to stand overnight) is 7.6. So going by that there is still co2 left in the water 24h later.
I have a lot of surface agitation as well after reading posts by plantbrain who said that surface agitation is a good way to increase oxygen in the water and therefore possible to increase the amount of co2 injected (a Dutch something or the other thread)
 
Hi all,
I'm still in Stockholm, so a bit of a quick answer. Basically the bubbles are irrelevant to the pH reading, although if they are small enough the plants can utilise them directly. Both pH meter and drop checker are measuring the small proportion of CO2 that has gone into solution as carbonic acid, the much larger proportion of gas remains as CO2.

As suggested earlier the pH meter is actually a specific kind of conductivity meter. The actual reduction in pH will depend upon the carbonate:CO2 equilibrium, which is why it is important that the drop checker contains bromothymol blue pH indicator in water hardened to 4dKH.

There is a more complete explanation in these posts: <pH probe calibration, question | UK Aquatic Plant Society> & <CO2 In the planted Aquarium | Page 2 | UK Aquatic Plant Society>.

cheers Darrel
 
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