# Another drop checker issue



## AndyVox (13 Aug 2012)

Right I'd been using premixed drop fluid that came with my drop checker, constantly lime green / yellow.
I decided to buy some bromo blue 0.04% and sme 4dkh water from aquarium plant food. 

I mixed the 4dkh in the checker with 2-3 drops of bromo blue, it stayed blue for 24hrs, confused I went back to my premixed solution, lime green within an hour. Tested the bromo blue with vinegar and it turned yellow straight away. I decided to give it another shot, again it's been blue for 8hrs, my injection rate for co2 is constant, it's on 24/7.

This has led me to three conclusions:
1) I'm using the wrong bromo blue. (I'm doubtful on this as it was directly from a well know scientific supplies company that advised the PH range was correct for this solution)
2) The water isn't actually 4dkh which is why it won't turn green. (maybe it would if I upped the co2 to ridiculous levels)
3) the premixed fluid I had before wasn't 4dkh and I've been under co2-ing my tank for the last 6 months (my plant growth and fish seem to suggest otherwise)

An help would be greatly aopreciated.

If I had a kh kit I could test the water, but I don't...


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## andyh (14 Aug 2012)

Hello

1. You dont state the type of CO2 system you are using?
2. Have you got flow around the drop checker?
3. Are you sure your co2 system is working
4. Have you checked for leaks. can you see CO2 bubble in your tank?


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## AndyVox (14 Aug 2012)

I'm using pressurised co2, fe style.
There is plenty of flow around the drop checker and it's in the same place as previously with the other checker fluid which turned lime green.
Co is working, bubble counter is the same as always and I can see it entering my Rex grigg style reactor and diffusing (glad I used clear pipe now!)
I upped the co2 to see if that was the problem which resulted in bubbles coming from the spray bar. Surface agitation is minimal, exactly as with previous checker fluid.

Cheers


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## Iain Sutherland (14 Aug 2012)

the mix of 4dkh and bromo needs to be quite precise, if too much bromo is added i always found it is difficult to change its colour, 1ml 4dkh to 1 drop bromo seems to be best mate.


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## AndyVox (14 Aug 2012)

I've Tried with one drop of bb and with 3-4 as per the instructions on apf's 4dkh. Neither work.
The bb that I've got is in the right ph range and should work. It reacts to vinegar very easily.
I've messaged John at APF and he's assured me that the water is 4dkh so it must be the bb, I've linked him to the product I'm using for bb so hopefully he can shed some light on it, then I'll let you guys know so nobody makes the same mistake as I have.
Must say as always brilliant customer service from John at APF, all the stuff I've ordered has always come quickly, been spot on and his reponse times are very quick!


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## Avit (14 Aug 2012)

Hi Andy,

You’re going to hate me for saying this but I think the mistake is not believing what the drop checker is telling you. I would guess this has all happened since maintenance and/or water change? Sometimes with a 300 litre tank CO2 can take an age to reach the previous levels after a 40% plus water change and especially if the flow has been altered slightly from maintenance/cleaning. Apart from the drop checker do you know roughly what levels of CO2 you have in the tank? Maybe try some other methods of testing CO2 and compare the results, none of them are accurate but I think you’ll be surprised with the findings.


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## AndyVox (14 Aug 2012)

Hi Avit,

I agree with you, it does take an age after a water change to get to decent co2 levels.
But... I water changed on Saturday, added new premixed solution to the drop checker (it was lime green/nearly yellow by 2 1/2hrs later) then decided on Saturday night to give the bb and 4dkh another go. It's been dark blue ever since.
The bb is the correct solution and John at APF agrees it should work.
So the only two things possibly affecting it are:
The 4dkh is not 4dkh.
The premixed solution isn't correct, the bb and 4dkh is fine and I'm well under 25-30ppm.

I'm worried about pushing the co2 if it isn't working because I really have no indicator that I'm over or under gassing.

Props to John at Aquarium Plant Food, he is sending me some more 4dkh and some gush premixed solution as a means test. Once I've got those I'll fill up two drop checkers side by side, one with my solution and one with the gush solution and see what happens.

In terms of bubble count, I'm using a JBL bubble counter, it's on 24/7 and im currently on 1.5 bubbles per second (the bubbles are fairly large on this model - I understand that this is a really crude measurement due to fluctuations between bubble counter models) does anyone with this bubble counter know approx how much should be going in, bear in mind that ALL the co2 is diffused fully into the water using my reactor, should I be adding more to a 300l?


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## GHNelson (14 Aug 2012)

Hi
The JBL bubble counter has a rubber O ring..... as it can be taken apart to be cleaned.
Check for leaks around the top of the bubble counter.
hoggie


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## spyder (15 Aug 2012)

AndyVox said:
			
		

> I decided to buy some bromo blue 0.04% and sme 4dkh water from aquarium plant food.



In the BB mix what is the other 99.96%? Would that possibly have any effect on results?


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## AndyVox (16 Aug 2012)

To mix bromo blue as an indicator solution from what I understand you mix the salts with ethanol so I imagine its the % of pure bromo blue in the solution?
Maybe someone with more chemistry skills can confirm?


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## hotweldfire (19 Aug 2012)

1.5 a second on a 300l seems low to me. I'm doing 3 a second on a 125l but I'm using a TMC counter. 

Sent from my MB860 using Tapatalk 2


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## stuwags (19 Aug 2012)

I've had probs with my drop checker too. I was using tank water with the JBL fluid that came with my co2 kit but recently switched to 4dkh water so I could be more accurate. However, with the recommended 1.5 ml of water and 3-4 drops it was bright yellow by lights on after running for 2 hours at 1 bps! It stayed yellow for a whole week. I didn't believe it so I decided to ignore it, increase the bps to 3 and watch the fish for problems. My fish were fine so I've switched back to using tank water and increased to 4-5 bps. I now get green at lights on and still no problems with the fish.

I don't know why this should be. Maybe the JBL BB fluid is different from a proprietary BB fluid ? I don't think I'll be trusting drop checkers in future and observe the tank instead!

My tank is 200L and co2 is dispersed via a tank length spray bar from the filter inlet


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## Nathaniel Whiteside (20 Aug 2012)

stuwags said:
			
		

> I've had probs with my drop checker too. I was using tank water with the JBL fluid that came with my co2 kit but recently switched to 4dkh water so I could be more accurate. However, with the recommended 1.5 ml of water and 3-4 drops it was bright yellow by lights on after running for 2 hours at 1 bps! It stayed yellow for a whole week. I didn't believe it so I decided to ignore it, increase the bps to 3 and watch the fish for problems. My fish were fine so I've switched back to using tank water and increased to 4-5 bps. I now get green at lights on and still no problems with the fish.
> 
> I don't know why this should be. Maybe the JBL BB fluid is different from a proprietary BB fluid ? I don't think I'll be trusting drop checkers in future and observe the tank instead!
> 
> My tank is 200L and co2 is dispersed via a tank length spray bar from the filter inlet



More likely is your tank water is harder
Than the 4dk solution. Thus your tank water make the drop checker less sensitive.


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## stuwags (20 Aug 2012)

True, but surely 4dkh water shouldn't register yellow 24/7 at 1bps for 6hrs a day. In theory shouldn't the fish be dead! and I certainly wasn't seeing rapid plant growth even with EI. 

I guess that ultimately the DC is only a rough indicator and shouldn't necessarily be relied upon.


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## AndyVox (20 Aug 2012)

My problem was definitely a problem with the BB. Apparently the 0.04% solution I had didn't work, it just stayed constantly blue. I've read a few people have had this issue before.
Using two drop checkers both with 4dkh, one with 3 drops of gush bb and one with my bb from the scientific company in question, from this I established that actually I had more than enough co2, turned it yellow so I've dialled it back slightly, but the none gush solution stayed blue the whole time. It should work in theory as it a PH indicator 6 - 7.6, but it just wouldn't change colour. It started blue which I think may have been the problem, I read something about it being used to stain cells. It did however turn yellow when in contact with vinegar.

Not sure why, but again. Thanks John at APF for the brilliant customer service. I think I owe him a big order as an apology! haha.


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## dafil (21 Aug 2012)

I found this :
 Bromothymol Blue (BTB)
Bromothymol blue is an indicator, a substance that changes color as the pH of a solution changes. Bromothymol blue is yellow in acidic solutions and blue in basic solutions.

    BTB can be prepared by mixing 0.1 g (a pinch) of bromothymol blue powder in 10 mL of a 4% solution of sodium hydroxide.
    Add 20 mL of alcohol and dilute to 1 L with distilled water.
    The solution should be deep blue.
    If it is green, add sodium hydroxide solution drop by drop until the solution turns blue.
    Bromothymol blue can be purchased from scientific supply houses. 

from here:
http://www.eduplace.com/science/profdev ... tions.html


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## AndyVox (30 Aug 2012)

What im using is definitely indicator solution, just doesn't seem to have the same PH indicator range as it claims to have. Turns yellow for vinegar.


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## Nathaniel Whiteside (30 Aug 2012)

AndyVox said:
			
		

> What im using is definitely indicator solution, just doesn't seem to have the same PH indicator range as it claims to have. Turns yellow for vinegar.



Funny you said that,
I had a Crappy Fluval dome shaped indictor, and then put my Cal aqua nano in next to it.

The colour was lime green in the Fluval but Cal Aqua one was quite dark green after being in for several hours.

Just shows how each solution can be individual.


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## AndyVox (30 Aug 2012)

Well in theory the concentration of the solution (drops to 4dkh) would make a difference I imagine.
There seems to be a vast difference between different brands. The lush stuff I have from APF is different to the stuff that came with my first drop checker from a side by side comparison.
What I don't understand is that this bromo blue solution is from a scientific supplier, so surely that should be more accurate than that from an aquarium product. You would think anyway.
At the end of the day a drop checker is a crude way of establishing how much co2 is in the tank, as much as I'd like to rely on it, I don't think you can. Much better to use it along with fish / plant response, set the co2 and leave it. The main problem with that is any plant changes would only be noticed over a week or more of consistent co2 levels.
I've come to the conclusion that the more co2 the better, so I've dialled it in just below the point where the fish gasp. I'm hoping after a few weeks of that it'll give good results. Again there are other factors to take into consideration, increased o2 massively increases the fishes tolerance to co2, and as plant mass increases so will the co2 uptake.
I never really appreciated what a balancing act planted tanks really are. I think I got lucky not to have had a few disasters with algae / dead fish before due to ignorance of the other factors.


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## dw1305 (30 Aug 2012)

Hi all,


> To mix bromo blue as an indicator solution from what I understand you mix the salts with ethanol so I imagine its the % of pure bromo blue in the solution? Maybe someone with more chemistry skills can confirm?


This is right, bromothymol blue is just a narrow range pH indicator. It is a weak acid and changes colour from yellow at pH6 to dark blue at pH7.6. It isn't very soluble in water, so you have to dissolve it in a solvent like alcohol. The amount of indicator isn't critical. You then use a 4dKH solution which allows you to make use of the carbonate:CO2 equilibrium tables to estimate how much CO2 you have. <http://www.tropica.com/en/tropica-abc/basic-knowledge/co2-in-the-aquarium.aspx>. 






You can make the 4dKH solution by dissolving 6g of pure sodium bicarbonate (NaHCO3) and making this up to 5 litres (in RO) to give you a 40dKH stock solution. Then using serial dilution 10ml of the stock solution with 90ml of 'fresh' DI will give you 1l of 4dKH reference solution (thanks to Aaron North for the calculation), or you can buy it from one of our sponsors.

If you haven't seen it this is all in Clive's tutorial: "CO2 MEASUREMENT USING A DROP CHECKER" - http://ukaps.org/forum/viewtopic.php?f=34&t=467



> so I've dialled it in just below the point where the fish gasp.


 You need to be very careful doing this, as fish can suffer sub-lethal damage long before they show obvious signs of distress <http://www.thefishsite.com/articles/103/the-importance-of-measuring-carbon-dioxide-in-aquaculture>. You also need to take into account that the response of all fish is not the same, and that fish from cooler, flowing water (like _Chaetosoma_) have a higher oxygen requirement than fish from warmer, still water. 
<http://www.freshwaterinstitute.org/...in_RAS_at_high_vs_low_CO2_in_RAS_AQUE_(2).pdf>

High CO2 levels in the water mean that the diffusion gradient from the blood in the fishes gill to the water is shallower and the blood haemoglobin loses CO2 more slowly. Because haemoglobin has an affinity for both oxygen and CO2, if CO2 levels are high less oxygen will be picked up by the blood. These are the "Bohr" and "Haldane" effects. 

cheers Darrel


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## dw1305 (30 Aug 2012)

Hi all, 


> 4% solution of sodium hydroxide. Add 20 mL of alcohol and dilute to 1 L with distilled water.
> The solution should be deep blue. If it is green, add sodium hydroxide solution drop by drop until the solution turns blue.


I should also have said that you don't want to add the sodium hydroxide (NaOH) if you make your own up for the drop checker, as the solution will be much too alkaline, and no amount of CO2 will make it change colour.

cheers Darrel


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