# Drop checker time lapse & CO2 schedule



## hotweldfire (22 Jun 2011)

Somewhat confused on the issue of when to have CO2 coming on vs. lights. Here's what I'm currently doing:

Solenoid on @ 10:00
Koralia on @ 11:00
Lights on @ 12:30
Solenoid/Koralia off @ 6:30
Lights off @8:30

Part of the reason I have the CO2 come on so early is that my crap regulator takes 45 mins to get the bubble count up to where it should be every day.

The other reason is that I have read on this forum that you should get it on before lights on in order to saturate the water before the plants start using it. Given my DC was never light green when lights came on I've pushed the CO2 back earlier in the day. Also, it's still light green at 8:30pm even though CO2 goes off 2 hours earlier. 

Here's the thing though. Doesn't a DC take two hours to register changes to the CO2 level? If so, then surely I should be looking for it to be lime green 2 hours _after_ lights come on rather than _when_ lights come on?

In which case I don't need CO2 coming on so early?


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## CeeJay (22 Jun 2011)

Hi hotweldfire


			
				hotweldfire said:
			
		

> Solenoid on @ 10:00
> Koralia on @ 11:00
> Lights on @ 12:30
> Solenoid/Koralia off @ 6:30
> Lights off @8:30


I run mine in a similar fashion (although mine starts a lot later in the day), with a 2 hour gap between CO2 on and lights on, but I leave the Koralia on until the lights go out.



			
				hotweldfire said:
			
		

> Also, it's still light green at 8:30pm even though CO2 goes off 2 hours earlier.


I run mine bordering on yellow these days and it's still that colour in the morning     The only time I see any major change in colour is on water change day, when it's exposed to atmosphere.



			
				hotweldfire said:
			
		

> Here's the thing though. Doesn't a DC take two hours to register changes to the CO2 level?


At least.



			
				hotweldfire said:
			
		

> If so, then surely I should be looking for it to be lime green 2 hours after lights come on rather than when lights come on?


I see what you're getting at, but it's always best to err on the side of caution and have CO2 at it's highest at lights on.


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## ceg4048 (23 Jun 2011)

hotweldfire said:
			
		

> ...Here's the thing though. Doesn't a DC take two hours to register changes to the CO2 level? If so, then surely I should be looking for it to be lime green 2 hours _after_ lights come on rather than _when_ lights come on?
> 
> In which case I don't need CO2 coming on so early?


Ummmm...no, this is kind of like asking when should I close the barn door. You have to close it before the horse gets out. I'm sorry mate but these are the early symptoms of test kit hypnosis. Do not fall into the trap of allowing the test kit to drive your objectives.

There is also a dramatic fall in the CO2 partial pressure despite the test kit readings. You can get an indication of this for yourself by measuring the tank pH at solenoid close and comparing it at solenoid open. You should find that the ph is lower at solenoid close than it is at solenoid open. 

Lights on is the most critical time of the entire photoperiod. In fact it's so important that most of our CO2 problems actually occur at this specific time - a low CO2 partial pressure and an inefficient uptake performance as the plant transitions from non-CO2 use to CO2 use. You actually need to have a very high CO2 partial pressure to force feed it into the plant in order to compensate for the short term inefficiency as the plant spools up. After about an hour or so the plant has warmed up sufficiently that it can deal with the baseline CO2 pressure. After 5 hours or so it starts to use less CO2, and by 8 or 9 hours of photoperiod it starts to shut down. It actually doesn't matter that much if CO2 is poor near the tail end of the photoperiod because the demand drops. But this is the opposite of what happens in an injected tank. The CO2 pressure is typically low on the front end of the photoperiod and is high on the tail end. This is one reason we have so many problems and why it's so difficult to resolve. It's a nuance that has a huge impact. The absolute last thing you want to be doing is to be messing around and choking the CO2 at lights on. Breakfast is the most important meal of the day.

So really, you need to forget about the dropcheckers quirky behaviour and concentrate on pumping up the pressure on the front end. Some day we might have a solenoid that has at least three programmable positions, Fully Open, Halfway Open and Closed , or, a regulator that delivers higher than set pressure for a short while, then returns to the set pressure.

Closed top tanks tend to retain the CO2 pressure significantly more than open top tanks, so different people have different CO2 partial pressure profiles throughout the day. It's hard to find a one size fits all because of the different dynamics occurring with the gas pressure.

Cheers,


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## Charlieh (23 Jun 2011)

Don't get so hung up about the drop checker time lapse. When you first put it in the water it takes a while for the liquid in the bulb to reach equilibrium with the aquarium water and for the indicator to change colour because this relies on the rate of gas transfer through the funnel and dissolution into the bulb liquid. However, once equilibrium is established, because the amount of fluid in the bulb is so much smaller than that in the aquarium it will respond to gas concentration changes quite quickly - it's the aquarium water that takes time to change. Try taking a yellow drop checker out of the aquarium water and see how quickly it goes blue.


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## niru (23 Jun 2011)

Hi Ceg

given all the shortfalls of CO2 DC, is there a topic discussing how much (bromo-blue + 4dKH water) reagent needs to be added for the DIY guys? Your excellent article on this topic mentions the JBL bottle, but people doing DIY and not realising the details might endup with differing color schemes, adding to the confussion!

I have tried a series of (interesting but useless) experiments about the DC in the tank to realise its fallacies:

 For guys doing diffusers for CO2, the mist in the tank is actually the gas which we hope will dissolve. Now if the DC is placed somewhere where these micro bubbles make entry into the air-gap of the DC, the color goes green-to-yellow in no time, though there isnt 30+ppm CO2 in the tank as such. And we might not realise it even! Since the mist is pure CO2, only a few bubbles suffice for this to happen.  I also noticed that if the DC is in the direct path of the filter output, then it takes more time for it to show the stable "true" color. Of course CO2 tends to escape from water inside the filters and the water coming out is slightly under-concentrated. Guess canisters with inline diffusers/atomisers/reactors on the outlet side are best way to dissolve CO2 for this reason, amongst many?

Another thing I tried is to put too less (& also too much) bromo-blue to the 4kH water giving dilute/concentrated reagent. Resulting color scheme is then affected due to (a) differing CO2 content in the 4KH water (different water amount in the DC), as well as (b) the amount of bromo-blue itself getting saturated post reaction with carbonic acid (differing concentrations of bromo-blue in same amount of 4KH water). Further on, I took 4dKH water with 3 different pH levels and of course the color change is affected even before DC is in the tank, which is expected for bromo measures pH. The reason I did this last thing is because the Dennerle long-tem CO2 indicator amplue is a ready to put into DC liquid with water already mixed. But it looks too blue to me telling me a pH slightly more than neutral, very unlike the JBL stuff you show in your article (which is, correctly, a bit greenish-blue for pH = 7). Their color scale then "correctly" show a CO2 of 0-10 ppm for this deep blue-color.

Perhaps all these are higher order effects, but they surely result in differing color identifications & hence deductions of the CO2 present in the tank. Sure enough to confuse who hasnt thought about the entire Matrix setup & stared long enough at the tank.

Having said all this, I do understand that this whole thing of DC measuring CO2 is a bit futile to get accurate ppm numbers, but its not in vain to roughly guess-timate if the tank is in right ball-park area with regards CO2.

-niru


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## ceg4048 (23 Jun 2011)

Hi niru,
          Yes, these are all excellent points. It's just very difficult to point out all these various effects in the article without losing the audience altogether. Certainly, moving the checker down to a lower corner of the tank might be an easy instruction to avoid having the bubbles interfere with the mean concentration value.

As regards the number of reagent drops, 2 or 3 drops ought to be sufficient regardless of checker type because the reagent Bromo Blue is fairly consistent. The real problem with many of the bubble shaped checkers is that they are transparent, and this causes troubles when viewing because the glass tends to reflect colors from within the tank itself, obviously the green from the plants, or whatever colors are in the background, impairing the color fidelity. That's why, in the article, I give major props to the humble JBL checker because of the white background strip which curtails the number of reflections and which therefore gives better color fidelity. Some people have painted the back side of the other checker brands with "white-out" or nail polish or whatever clever substance to enhance viewing the color.

Cheers,


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## Charlieh (23 Jun 2011)

You're overthinking it niru lol


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## niru (23 Jun 2011)

Charlieh said:
			
		

> You're overthinking it niru lol



Hi Charlieh, of course it was over indulgence! But I loved doing all of it, if not for anything else, simply to glimpse how the pioneers must have thought through all the minute steps....   


Cheers
Niru


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## plantbrain (24 Jun 2011)

I do not suggest DC's, never really have.
they have been around since I got into CO2, Dupla had them.

With reference KH solutions, this made it a bit more precise.

Still, I think using the pH/KH table, then from there, adjusting upwards, tweaking based on a fish/plants with good current and O2, is the best method. Must be done very slow and progressively. Close observations etc must be made during the adjustment tweaking period.

I made a KH reference cell that could be placed on flat tipped pH probe recently that matched the 3000$ unit I have, which is essentially the same thing.

I have to convert the readings, but this is not bad.
I spent a fair amount of time and prototypes to make them.
But now I've got 2 of them to use all the time and can data log.
CO2 is not what we like to think and say it is.

I think the levels are much higher than many like to claim.


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## Garuf (24 Jun 2011)

Tom, can we get pictures of the ph probe dealie? 
Also, can you clarify on the ph/kh table method, I assumed that with most hobby grade ph test it would be too inaccurate?


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## niru (24 Jun 2011)

Why arent there any titration based hobbist test-kits for CO2 that will measure the carbonic acid and/or carbonate/bicarbonate levels thereby yielding the total CO2 content for the given pH, kH levels in the tank? One could get water samples from different areas of the tank and test the distribution as well...

Perhaps a "stupid" question with obvious answers that I am unaware of   :?: 

-niru


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## hotweldfire (24 Jun 2011)

Clive, please don't tell me you're saying that the DC is another useless bit of test kit. I hear what you're saying - have the CO2 schedule setup to meet your objectives which is to get high levels at start of the day. But I'm not (intentionally) looking to have the DC change my objectives - just to test whether I'm meeting them. 

Why is the thing quirky? I understand, as niru points out, that the position of it will drive it's colour because of both different concentrations of co2 around the tank and the possibility of co2 bubbles entering it. This is why I have it low down at the opposite end of the tank from my diffuser (incidentally also the opposite end from my filter outlet).

I don't expect the thing to give me an accurate ppm reading. I do expect it to tell me how the co2 concentration is changing. With a dodgy regulator and a bubble counter that often stops working this is quite important. 

Charlieh, are you saying the time lapse will only be occurring when changing the solution? I.e. if it's been in the tank a day it will respond to changes very quickly?

Tom, I stopped using ph/kh tables when I read about other influences in the tank (wood, substrate etc) affecting the ph. Also, as Garuf points out, the accuracy of ph test kits. Was that a mistake?


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## niru (24 Jun 2011)

Hi hotweldfire

I guess you could continue using the DC so long as its only an indicative measure of the CO2in the tank. All the caution etc is for mainly to realise that the actual colour you see in the DC need not accurately reflect the CO2 in the tank in the ppm sense. But surely blue isnt 30 ppm, nor is yellow a 20- ppm. Account for the DC position, time lapse effects, etc and you are in good ball park area. So let DC only indicate the direction, dont let it drive your final goals.

Moreover as Tom and Clive have mention, measuring CO2 is notoriously difficult. Talking only about the DC, a simple web search will show that bromo-blue is a reasonably good indicator since it works in the pH range we are mostly interested in, and that its color changes are distinct enough to visibly see. Maybe someone with chemistry research background can come up with a better indicator that has higher colour resolution & differentiation to suit the tanks. I read that theres some 2 solution ethanol based titration thing one could do (its done in chem labs, though not sure of aquariums).

Also, spending more time with aquarium inmates & keeping a tab on CO2 related plant/algae issues soon renders the DC method a distant 2nd. Then on DC serves mainly as an accompaniment.

Experts can chip in here & we all would benefit!!

-niru


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## Charlieh (24 Jun 2011)

> Charlieh, are you saying the time lapse will only be occurring when changing the solution? I.e. if it's been in the tank a day it will respond to changes very quickly?



Exactly, or when it's removed from the aquarium water or anything that upsets the equilibrium. It's establishing the equilibrium that takes time but once coupled it will change colour as the tank CO2 concentration changes (which isn't very quickly under normal circumstances - hence the 2 hours before lights on routine). It's like any detector or probe (a thermometer for instance) - they have to be given time to settle before taking a reading - some just take longer than others.


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## hotweldfire (24 Jun 2011)

Thanks both. Niru, yep, I want it to act as an indicator for direction of change rather than an accurate test of ppm.

Also, does anyone else have a problem keeping the inside of their's clean? I'm constantly getting build up of indicator solution stuck to the bottom of the inside of the bulb, even though I wash it out and refill every week. Means I can only use the upper section of what's filled as the base always looks lighter than it should.


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