Co2 And Kh Question?

[saz326]

I have a permanent test that displays 3 colours depending on the availability of CO2 in the tank water. The solution in the test unit is blue for low CO2, Green for correct CO2 and yellow for too much CO2.

Can I ask, Do these units tell you the concentration of CO2 in the aquarium water - independant of KH and pH readings?

 

[Colin_T]

yes they should do. Most test kits are for a single item only, ie: KH, PH or CO2. They give you results for that particular item regardless of most outside factors. There are exceptions to this rule but only a couple.
eg 1: nitrate test kits will read nitrite as nitrate.
eg 2: hydrometers for measuring salt levels in marine tanks are affected by temperature. Therefore they are set to give an accurate reading at about 24C. Outside this temp they can vary on their accuracy.

A CO2 tester should give you the CO2 levels in the tank regardless of if the water is soft and acidic or hard and alkaline.

 

[aaronnorth]

Drop Checkers

Everything you need to know is in the above guide

 

[SuperColey1]

You need to read Aarons pinned thread on this. The permanent CO2 test is actually a permanent Ph test in reality and is used with a known reference solution to correlate the Ph level to a CO2 content. the 'manufacturers/retailers' seem oblivious to this in their instructions!!!

Aaron's pin will explain all.

 

[saz326]

Thanks both for your help on this.

Am gonna have a good ol' read!

 

[saz326]

Just read the pinned jobbie - very informative... but not quite what Im after..? (I'm a pain)

My permanent test asks for the water diluting the test solution to be tank water - I assume this is just so that the first immediate reading is as accurate as possible (as they the devices take a while to react to changes in CO2)

Its made by "Red sea" and consists of a drop checker a test solution and instructions.

The test solution is coloured Orange and is labeled as flammable - so I Have no idea what it is made of. (and Im a chemist!)

You are requested to add 1ml of tank water to 2 drops of the test solution - which then goes blue with my alkaline tank water (so it could be pH based). It appears blue at "low" CO2, green at "good" CO2 and yellow at "too much" CO2.

The reason I am trying to figure a few things out is that I have read that the KH of your aquarium water can mean that the level of CO2 you try to achieve can end up being dangerous to the fish.

I am aware that the amount of CO2 that can disolve in your water is dependent on the KH of the water (more carbonate ions means that the water can sustain more acidic ions i.e. CO2)

so - is the test ket telling me how much CO2 is dissolved per litre (and therefore how much is available to the plants), or is it telling me the CO2:Carbonate ratio - which could end up with me poisoning my fishies, but having fantastic greenery?

I wish the instructions were better!

P.S. I live in a very hard water area. The Water supplier (Three valleys) has listed our supply as being 385mg/l total hardness. "Clarke" hardness of 27 units. 154mg/l calcium.

 

[SuperColey1]

As I said in my post:

the 'manufacturers/retailers' seem oblivious to this in their instructions!!!

Hence you said

My permanent test asks for the water diluting the test solution to be tank water - I assume this is just so that the first immediate reading is as accurate as possible (as they the devices take a while to react to changes in CO2)

This is because the tank water contains many other things that reduce Ph thus giving you a false reading. 4dKH reference solution will not have these in it and therefore as long as it is changed every couple of weeks will change from CO2.

It is more than likely a bromo blue Ph test solution relabelled as something else and packaged in a much smaller bottle. this should be OK to use with the 4dKH

Just put 1ml 4dKH with 2 drops of the 'test solution' and it will start to read the Ph change from CO2 instead of other acids that are in the tank water.

You can get Ph crash with extremes of high or low KH. The vast majority of people will not see these levels unless they have put something in their tank to cause it!!!

You got the CO2 dissolving part wrong here. If 2 people have the same Ph but one has higher KH then the person with the higher KH is likely to see a smaller Ph drop than the person with the lower KH. therefore if you both use tank water in your drop checkers and assume 2bps = 30ppm the person with the higher KH may still see blue and think they need to turn the CO2 up!!! If you both use 4dKH reference then you are both looking at the same reading. Remember this is a CO2 indicator but is in essence a Ph test.

The test with the correct reference solution wil tell you the ppm (part per million) that the CO2 is of the tank water. The test with the tank water in will just tell you the Ph change of the tank water outside but that can be due to many other things!!!

p.s. I also live in a very hard water area. Isn't calcium and magnesium GH and not KH??? It's the KH you want to worry about in relation to this subject.

AC

 

[saz326]

This is because the tank water contains many other things that reduce Ph thus giving you a false reading. 4dKH reference solution will not have these in it and therefore as long as it is changed every couple of weeks will change from CO2.

Just put 1ml 4dKH with 2 drops of the 'test solution' and it will start to read the Ph change from CO2 instead of other acids that are in the tank water.


p.s. I also live in a very hard water area. Isn't calcium and magnesium GH and not KH??? It's the KH you want to worry about in relation to this subject.

AC

Thanks Supercoley1.

After I had re-read the third time (and Im supposed to have an Chemistry degree!!.) I realised what the wording was actually saying. I think I got "hung up" on the manufacturers words "CO2 indicator"... liars! I couldnt see that the indication of CO2 is basically a side effect of an indication of pH.

Going forward, I shall use a 4dKH standard, and test from there on.

Yep - you're right. carbonates are GH.. I had assumed carbonate hardness (KH) was "carbonates" . Nope. It is the buffering effect of the carbonates, and not the carbonates themselves.

This aquarium malarky is an 'arf confusing at times. Shall go and sit in a dark room for a few minutes.

Thanks for your patience

 

[SuperColey1]

It used to be called a 'permanent CO2 test' which of course is wrong. These days most have changed to 'indicator' which indeed it is. Even with tank water it 'indicates' the level of CO2.

Remember the word indicates doesn't mean 'accurate result' Its more a case of 'could mean'.

Then there are the majority who don't know much about modern planted methods and are just keen to sell anything they can without understanding why people are using it. lol

AC

 

[aaronnorth]

My permanent test asks for the water diluting the test solution to be tank water - I assume this is just so that the first immediate reading is as accurate as possible (as they the devices take a while to react to changes in CO2)

It must be 4dkh solution, other acids in the water affect the ph (lower it) so you get dodgy readings. Acids such as nitric and humic, or even phosphate can affect the readings!!

The test solution is coloured Orange and is labeled as flammable - so I Have no idea what it is made of. (and Im a chemist!)

More than lilley bromothymol blue - can be found in the low range of ph test kits if you need more.

The reason I am trying to figure a few things out is that I have read that the KH of your aquarium water can mean that the level of CO2 you try to achieve can end up being dangerous to the fish.

Having a low kh makes it easier to inject/ dissolve CO2 into the water, and having a high kh makes it harder, however for what we call 'high' in this hobby it barely makes a difference (unless you have like 30dkh+ ). If tank "A" has tap water measuring ph 7.2 and kH 10 ( high levels of carbonate and bicarbonates) then 30 ppm of dissolved CO2 may only cause his pH to drop to 7.0

Meanwhile Hobbyist "B" has tap water also measuring 7.2 but kH 6. More acid can form in his water (because of less carbonate and bicarbonate levels), so 30 ppm dissolved CO2 in his water will result in a pH drop to 6.8.

so - is the test ket telling me how much CO2 is dissolved per litre (and therefore how much is available to the plants), or is it telling me the CO2:Carbonate ratio - which could end up with me poisoning my fishies, but having fantastic greenery?

drop checkers tell us the "ppm" of CO2 in our water.aim for 25-35ppm

HTH, Aaron

 

[wolfwolf]

I just wrote an email to red sea since I have recently purchased their co2 indicator. I asked for them to comment on this discussion. Could be interesting.

 

[SuperColey1]

They will say what all manufacturers would say 'We spend £s on testing and research. who do you think you should trust? the experts or the hobbyists'

If they do say that then the following thread is asking the very same question as we are answering here on the very same drop checker and this is from the barrreport which is basically THE gospel of modern planted tanks!!! If they still want to argue they are right they should put in an appearance on there and explain/blag their reasons why.

Pay careful attention to page 4 where the 'hobbyists' explains why the 'experts' have got their science wrong in their instructions/assumptions. Ignore anything I say in the thread though as you can obviously see from my signature below that I do not know how to grow plants

<a href="http/www.barrreport.com/co2-aquatic-plan...wn-checker.html" target="_blank">http/www.barrreport.com/co2-aquatic-plan...wn-checker.html</a>

I have to add though that as I said before this is not a RedSea problem. It is an industry wide problem and all DCs are sold with the instruction to use tank water.

AC

 

[wolfwolf]

Not doubting your ability to grow a nicely planted tank. Just want to see the response from Red Sea. Kinda mad I spent $12.00 for a crappy way to "indicate" my co2 level.

 

[SuperColey1]

Not doubting your ability to grow a nicely planted tank. Just want to see the response from Red Sea. Kinda mad I spent $12.00 for a crappy way to "indicate" my co2 level.

I use glass ones that I bought from hong kong on ebay for £4 each. Then I use 4dKH and PH kits in them. Useful but just don't trust manufacturers to keep up to date with science. They are in the business of selling (and marketing their items.)

By the way, when I said I couldn't grow plants, it was tongue in cheek

AC

 

[saz326]

Not doubting your ability to grow a nicely planted tank. Just want to see the response from Red Sea. Kinda mad I spent $12.00 for a crappy way to "indicate" my co2 level.

..Guilty too there. Except translate the $ to £ and add 1.50!!

There were no CO2 liquid test kits - and now I know about 4dKH solutions I wonder whether I would have had the same problem using them.

Huff.

Great idea with the e-mail to red sea.