Drop Checker

[sid_zie]

Hi all

I wasn’t sure whether to post this in the science section, but I decided you were all smart here so should be able to help.

I started my first planted tank a little while back, I’ve got a DIY CO2 kit going. When I started it I made sure the mix was not producing too much CO2 and I’ve gradually been increasing it (as I have been having a little algae trouble). Now I was thinking about getting a drop checker (or some other CO2 indicator) so that I don’t start putting too much CO2 in.

I’ve seen the drop checkers and just wondered how they work. Does the indicator solution read the pH of the water? (more CO2 would make the water more acidic? is that right?)

Thanks in advance

 

[Dave Spencer]

The purpose of the drop checker is to give a good indication that the tank CO2 levels are running at 30ppm. It is done by adding a few drops of Bromo Blue liquid to the bulb on the left of the dropper ( I actually use the drops from my Nutrafin Low Range pH test kit). Then you need to add a few drops of reference solution at a carbonate hardness of 4dKH, which is basically DI water with some BiCarb added until 4dKH is reached. The 4dKH reference solution is pure, without any unwanted influence on its pH, unlike using tank water, so adding the test drops to the solution we should see a dark blue colour, indicating a pH of 7.6.

When the dropper is fitted below the water level in the tank, an air gap is trapped between the tank water surface and the reference solution. What happens now is that the amount of CO2 in the tank water will, over the period of an hour or two, equalise with the CO2 in the dropper air gap, and thus affecting the reference solution. The colour of the reference solution should change from blue to green, with green corresponding to a pH of 6.6 on the Nutrafin chart. Correlating a carbonate hardness of 4dKH against a pH of 6.6 (a pH drop of 1) and we get a CO2 level of 30ppm. If the solution remains blue then CO2 levels are too low, and if it goes beyond green and turns yellow then CO2 levels are getting too high.

It is possible to make the 4dKH reference yourself, if you have the means:

Add 6g of pure Sodium BiCarbonate to 5l of DI water to give you a solution at 40dKH.

Mix 10ml of this solution with 90ml of DI to give you 1l of 4dKH reference solution.

Dave.

 

[sid_zie]

Thanks

That makes a lot of sense. Does the indicator solution have to be changed regularly?

Also, are there alternative methods to monitoring CO2 levels? Would the drop checker be a recommended way to keep a check on the levels?

Cheers

 

[xxBarneyxx]

The reference solution is supposed to be changed once a week I think. However I change mine about once a month and know a lot of others do the same.

Drop checker is the cheapest, easiest way to check CO2.

 

[sid_zie]

Ok, excellent. I will have to put one on my shopping list for the weekend. Are there many different makes?

Thanks Dave and Barney

 

[xxBarneyxx]

Yeah there are loads but all work the same way. I got my glass one off Ebay for about £4 which looks exactly the same as the ADA ones which cost about £50. The 4dkh solution is just easier to buy

Just to make sure you get the right stuff you need:
Drop Checker,
4dkh reference solution
Bromo Blue liquid PH test solution (I used the stuff that came with my JBL drop checker and it works fine).

When you get it put 3-5ml of 4dkh in the drop checker and add a few drops of the PH test liquid and then stick it under the water (about halfway down the tank is best).

 

[Themuleous]

Get a cheap one as chances are you'll break it at some stage! I know I have! And you'll kick yourself the one you break is a £45 ADA one! Get one from here http/stores.ebay.co.uk/AquaticMagic_CO2-...4QQftidZ2QQtZkm

I and many others have used him, hes very good

Sam

 

[SuperColey1]

I read someone suggest weekly chnaging the other week but I've always read previously 3-4 weeks. Don't know where every week suddenly came from (points finger of suspicion at seller starting rumours. lol)

Andy

 

[Themuleous]

Yeh monthly is fine

 

[sid_zie]

I think the idea of going for a cheap one is a good one. Yeah, knowing me I am fairly likely to break it at some point. And changing the solution once every 3-4 week, got it.

Thanks all.

 

[Neo8223]

Monthly he says I have never changed mine and thats 3 months! Doesnt make the slightest difference. At the end of the day, it is a liquid at room temp and as it is in the water, it is a constant 25-27, and with my A level C at chemistry, i see no problem having it for long periods of time.

I predict that below, someone is going to proove me wrong lol.

 

[nry]

Is there no chance of the chemicals in the check liquid (the bromo blue in my case) going 'off' or becoming less accurate over time? How about changes to the water, algae or similar things affecting the water chemistry?

 

[Dave Spencer]

Is there no chance of the chemicals in the check liquid (the bromo blue in my case) going 'off' or becoming less accurate over time? How about changes to the water, algae or similar things affecting the water chemistry?

I am just surmising, but I think the bright lights we use could have an affect on the indicator at some time, ageing it prematurely. I generally change mine every month, but have been known to forget.

Dave.

 

[SuperColey1]

And what about the reference water staying at 4dKH?

It is not in a closed unit and snails for one can crawl up and bring tank water into the solution.

I once had to spear a molly fry to get it out!!

Therefore over time the water could get more and more contaminated therefore not being the 'reference' it was riginally intended to be. Hence flushing and replacing so you are back at 4dKH

Just a thought

Andy

 

[sid_zie]

Thanks once again. Everyone is very helpful.

I have ordered one from ebay - since i couldn't find one in my LFS (not really a big shock - but any excuse to go and look round).

So, changing the solution about every 3-4 weeks will be fine? And leaving it longer it wont actually stop working, but will just have more chance of being contaminated and so being less accurate? I'll aim to change it once every 3 weeks, and by the time i forget it will probably be about 4.

Sid