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CO2 level

Saman

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10 Nov 2020
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London
After seeing my plants decline over the past month I've realised that my CO2 levels are too low so I am now in the process of trying to figure out the right level. I'm finding it overly complicated though! I measure the ph in the morning before the CO2 starts and it's 6.6. After 2.5 hours it's about 6.2 and the drop checker is a mid green. This seems really odd to me as I'm using mostly RO water with some tap, there's about 50l of water in the tank and there's about 3 bubbles a second of CO2. If I then measure the ph in the afternoon it's about 5.6 and the drop checker is yellow so it means I can't increase the CO2 anymore to get a point drop in the morning - and now need to decrease levels to keep things safe for the fish throughout the day. Can anyone help me figure this out? How can I get this point drop first thing before lights on and for it not to continue to drop? I'm posting the issues with my plants for reference - every type of algae in small amounts (and snails) and browning leaves. Details of my tank are in the journals section - I'm not sure how to post here. My light is currently on 70% for 8 hrs a day. Thank you
 

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Nick potts

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Hey Saman.

Are you noticing the fish acting unusual with the yellow drop checker (gasping at the surface etc)? If not then chances are the CO2 level is not to high.

As for the 1 point drop, if you don't want to increase the rate you can increase the duration and have the gas come on earlier (mine comes on 3 hours before the lights)
 

Saman

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No they seemed fine... I’ll try 3 hrs before lights on tomorrow but I think it needs a lot longer to reach the point drop.
 

Zeus.

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A stable pH from lights on till CO2 off is the goal, best to to find tank pH take a clean glass of water out of tank and leave 24hrs then take pH of glass, if you take tanks pH before CO2 on if the tank hasn't fully degassed (my 50L never does over night).
Once you have the tanks pH (from glass) you will have your target pH, getting it stable from lights on till CO2 off is the tricky part and the only part where you adjust the injection rate - it can take many adjustments, taking pH every 30 mins (create pH profile).
Once you have it stable form lights on till CO2 off -Do NOT adjust the injection rate again.
Then you just time how long it takes from CO2 on to reach your target pH.
If you change anything, check the pH profile again
 

Saman

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Ok thank you - so I take a glass of water from tank (at any point) and leave for 24hrs to find tank ph. I then aim to reach this by the time the lights come on - so this means the tank ph after 24hrs is lower than the ph in the morning before lights on & co2? How do I keep the ph stable through the day? Is it changing at the moment because I’m injecting too much co2?
 

Zeus.

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The 24hrs old glass of water is the tanks pH lets say it 'happens' to be 7.2pH
Lets say your after 30ppm CO2 which is approximately a 1.0pH drop
So target pH is 6.2pH.
example-
You turn CO2 on , wait say 2hrs, then lights on, take pH say its 6.2pH wait 30mins, take pH, say its still at 6.9pH and keep repeating this and at 2 to 3 hrs after lights on the DC changes to a darkish green, the DC stays that colour and the pH stays at 6.9 until CO2 has gone off, the result is a stable pH form lights on till CO2 off. You may not have reached your 30ppm CO2, but your [CO2] is stable - the stable pH/[CO2] is more important than the 1.0pH drop or 30ppm.
This is very unlikely to happen, getting a stable pH is hard, the pH will increase when lights come on or the pH will decrease, I class a stable pH if the pH doesn't change more than 0.1pH from lights on till CO2 off- which take some doing -many try's, with each try on a different day - hence it can take weeks or months to get it right, adjusting BPS/injection rate up/down
Once you have it stable from lights on till CO2 off and your happy with the pH drop the last bit is easy. Wait till next day again, then just time how long it takes to reach your target pH, this is something that can not be changed and is out of your control, -( unless you have duel CO2 injection and twin solenoids and timers - having these makes the whole CO2 setup much easier to do, at a much bigger setup cost).

Having a Stable pH profile is only half the CO2 story, you also need good flow in tank, Flow is King in the CO2 enriched tank, if the flow isn't good enough [CO2] in the tank will fluctuate at different levels/areas in the tank especially at the substrate/carpet level, getting the flow good first with good surface agitation is where many folk go wrong and they enter a world of pain with their tank.

Once I have a pH profile I am happy with I check it every so often (daily at first then weekly then move on to months) you don't have to do the whole pH profile at this stage, pH at lights on and pH at CO2 off, if within 0.1pH drift I am very happy.

Also trust your DCs colour change a light green is 30ppm, yellow can be dangerous to livestock.

Get the Flow right first
------------------------
DC - Drop Checker
[CO2] - Carbon Dioxide Concentration
 

Saman

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Wow thank you this is really helpful. Can I ask what you use to measure ph? I have a pen but it never settles on an exact number so is hard to judge. What happens with water changes? Surely this will impact things?

With the flow I queried this a lot at the start as the h’ra at the back don’t sway but was reassured it was fine. Given what you say I think this does need to be looked at. I use a Lilly pipe at the front and the tank is uncovered too - I’ve read these things are problematic but I can’t change them… I did put a skimmer in but it sucked a fish in and killed it so I stopped. It’s a small tank so I’m not sure what else to do. What would you advise? Can you see the tank in my journals? It’s pretty small.

I reduced the bubble count yesterday so hopefully the drop checker won’t turn yellow today. I’ll keep a close eye on it all whilst I wait for the ph result from the glass. Good job I’m working at home!!

Thanks again
Sam
 

foxfish

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A basic PH pen is ok but I treat them as a disposable aid as they dont seem to last or stay reliably for long.
A new £12 PH pen, freshly calibrated, seems to work well enough for a short time and might last longer if the probe is regularly and carefully cleaned with RO water ?
 

foxfish

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In a small tank a lily pipe should be fine but finding the best position might take a bit of experimenting.
The flow rate is really important and may also need a a bit of adjusting.
You can try adding tiny amounts of food into the flow and see how it behaves, obviously you want to see the particles reach every corner of the tank.
 

Wolf6

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You may not have reached your 30ppm CO2, but your [CO2] is stable - the stable pH/[CO2] is more important than the 1.0pH drop or 30ppm.
This is very unlikely to happen, getting a stable pH is hard, the pH will increase when lights come on or the pH will decrease, I class a stable pH if the pH doesn't change more than 0.1pH from lights on till CO2 off- which take some doing -many try's, with each try on a different day - hence it can take weeks or months to get it right, adjusting BPS/injection rate up/down
Once you have it stable from lights on till CO2 off and your happy with the pH drop the last bit is easy. Wait till next day again, then just time how long it takes to reach your target pH, this is something that can not be changed and is out of your control, -( unless you have duel CO2 injection and twin solenoids and timers - having these makes the whole CO2 setup much easier to do, at a much bigger setup cost).

Having a Stable pH profile is only half the CO2 story, you also need good flow in tank, Flow is King in the CO2 enriched tank, if the flow isn't good enough [CO2] in the tank will fluctuate at different levels/areas in the tank especially at the substrate/carpet level, getting the flow good first with good surface agitation is where many folk go wrong and they enter a world of pain with their tank.
This mirrors my experiences, flow and stable CO2 are more important then hitting that 30ppm, I aim for 20ppm but continuously check flow and maintain CO2 level, cutting back plants/cleaning pipes whenever needed to maintain that stability. I only have issues when timers fail or CO2 runs out and I dont notice in time, meaning that stability is affected.
 

Saman

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Thanks all - it’s tricky for me to move the Lilly pipe as there are two big pieces of wood either side and I’ve cut all the tubing precisely to work with an inline diffuser and positioning. I’ll watch how the food circulates and report back. And I thought using co2 would make my life easier!! It’s been interesting (and disappointing) to see that the tank start really well - so vibrant and fast growing - and now there is slower growth, plants fizzling out. The ludwigia super red has pretty much given up after being so stunning in the first month. It started when I switched to RO weirdly but I guess that’s a whole different story…
 

Saman

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This is my ph pen - it’s rubbish…
 

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Wolf6

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This is my ph pen - it’s rubbish…
I just use regular drop checker with aqua rebel fluid 20ppm, I've come to trust that more then using tank water, but I'm sure others here might say its worse. I dont know what is true, just that this has given me personally enough results without putting in more effort then I want to invest. I'm lazy :) I also have a twinstar nano which allows me to see the full flow of water through the tank, so I can spot spots with less flow.
 

Zeus.

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A basic PH pen is ok but I treat them as a disposable aid as they dont seem to last or stay reliably for long.

I agree with @foxfish all the way, I do have a Hanna pH pen wasn't cheap, but a cheap one will do the job, it doesn't even need to be accurate IMO as its the pH drop we are after not the actual pH of the water, can can also use pH test strips as some of them are pretty dare good @X3NiTH or @dw1305 will probably know of some good ones, its the fast result that counts, I cheap pH pen is much-much better than non - especially on your first go at CO2 injection. DC are great for the colour change which is your main guide to [CO2], but slow one of main takes about 3hrs so its poor of doing pH profiles but looks good on tank and great for telling me tank needs a trim-which is silly really as the plants sticking out of water does that also 😅

What happens with water changes? Surely this will impact things?

Yes, well spotted :clap:, the tap water will have a higher [CO2] than your 24hr water in glass, I have read that folks see better growth after WC day with fast growing plants. I did some casual experiments with CO2 injection and did find that if the WC is close/next to CO2 coming on the pre CO2 time could be shorter than normal and still hit the same target pH. So I allow for this on WC day.

On my 500L tank I have duel CO2 injection and twin solenoids, twin CO2 reactors and a PLC which does all the timing, I use to use a pH controller also ( pH controller is a waste of money IMO),
I have a crazy injection rate

Which gets ( or has got in pass) a 1.4pH drop in less than 30mins, use to shorten the pre CO2 on time 10mins if I had just done a WC.

Having a PLC does give industrial reliability with timers and just a completely different level of timing control - mainly thanks to @ian_m with his LOGO!Soft Comfort programming he did with 'TankyMyTank' design, you adjust one time and it adjusts all on off times - its a work of art IMO. Only downside is PLCs are not cheap.

Once CO2 injection is mastered the need for a pH pen and pH profile isn't as great and many experienced scapers don't use them, but still a great tool IMO.

I also have a twinstar nano which allows me to see the full flow of water through the tank, so I can spot spots with less flow.
:thumbup:, agree 100% great for accessing flow, especially when using CO2 reactors
 

erwin123

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I have an Apera pH pen and i have been calibrating it monthly in 4.0 and 7.0 solution. Each time I calibrate I find that the pen is only 0.1 off from the 4.0 / 7.0 reference point. Therefore, I presume it is reliable enough for 'consumer' usage. It has almost 4,000 reviews on amazon so it appears to be a pretty popular product. They also have a more expensive model with replaceable probe.

Amazon product
 

Saman

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I've just checked the flow with food and it's pretty good apart from skipping the extreme back right corner. I increased the amount of time for the co2 coming on before lights on last night and after 3 hours the DC was only a mid green by lights on. But I know if I increase the co2 injection further - as I tried yesterday - it will go yellow later today. Now after 3.5 hrs the DC it's only just turning that limey green - I reckon it takes 4/4.5 hours. How is that even possible with RO water and 2/3 bubbles per second? I'll wait for the ph reading from the glass before stressing about this further.

Thanks for the advice re the pen - you don't have to calibrate them with RO when you buy them do you? Just after a period of use?

On the WC, I use RO mixed with tap - 90% RO 10% tap as advised here. I do think there's a connection with my poor plant growth and the switch from 100% tap to this. I understood most plants prefer soft water - hence the switch (and the livestock I want to keep) - but that hasn't worked out for me. Maybe I need to look at the fertiliser too? Feel like starting again might just be easier - except I have a lot of very happy shrimplets and paskai rainbowfish!!
 

Zeus.

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Each time I calibrate I find that the pen is only 0.1 off from the 4.0 / 7.0 reference point.
I really calibrate mine and just use the ph drop or stable pH from lights on till CO2 off and the DC colour change. If the ph pan says a different pH the next day I ignore the difference again going off ph drop or stable pH from lights on till CO2 off and the DC colour change.

Feel like starting again might just be easier

Except you may make the same errors, if you can solve the issues you learn more and know you have corrected the issues.

Maybe I need to look at the fertiliser too?

What are you using ATM ? APFUK starter kit is a great start to cheap/DIY ferts
 

Saman

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Yes true! I was going to rescape my other tank and add co2 so I can use that as a learning experience too. I'm using Evolution Aqua 'the aquascaper' all-in-one fertiliser about 3 mils per day.
 

Zeus.

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Evolution Aqua 'the aquascaper';)

George Farmers fert . When myself and @Hanuman did the IFC Calculator, I did try and find the ppm weekly yields for the product, so we was unable to see/compare/clone the fert so it is a bit of an unknown ATM until we get our hands on the data analysis of the product. Until then my advise is DIY ferts if over 100l tank, if under 100litres it would be TNC complete in the UK and Thrive in the USA. We do still keep our eyes on products that give good value for money, as plants don't care about brand 👍
 

Saman

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That's interesting - I was recommended it so thought I'd try it out. My tank is about 50l discounting hardscape etc so I will try TNC complete. Thank you!
 

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