# Other Aquarium Forums > Equipment and Accessories >  How to read Sera CO2 testkit?

## EvolutionZ

hi guys, anyone is using the sera co2 test kit?
i just bought 1 at NA 2 days ago.. set-up my tank yesterday and started using it..



i set my co2 BPS at 2. base on the test kit. blue = too much co2, darkgreen = good co2 level and light green = too little co2.
my co2 is dissolved via a ADA beetle replica ceramic diffusor. produces alot of very very fine bubbles. and blown around the tank by my rainbar. i would say 80% of the co2 is successfully diffused.

anyway.. its been half a day upon running this test kit, but the colour was at yellowish greenish colour(same colour as the liquid that was given to drop 3 - 4 drops into the co2 indicator.
so i up my co2 to 3bps. after running for hours.. the colour remained.. i deicded to pour away the current water in the indicator. and redo the test again.

so today, im back from school and i still see yellow colour despite my co2 running 24/7(manual regulator on co2) i decided to once again up my co2 to 4bps.
so from 2+pm till now.. my co2 has been 4bps but the co2 test kit indicator was still at yellowish colour(the 2 photos i provided on top, just taken minutes ago.

i believe my endlers inside the tank helping to cycle the tank was gasping for air.. 


so now i tuned down my co2 back to 3bps.. is there anything wrong with this test kit? or do i have to wait till the colour change? i check for the expiry date and the closest date for expiry was 02.2012 which is 4years later.

i always thought that sera test kit was one of the best.. but seems like it isn't?

can anyone help? thanks in advance.

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## EvolutionZ

nobody can help? from when i post till now still same colour leh :Sad:

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## Shadow

Normally blue means too little CO2 and yellow is too much CO2. Your tester label probably telling you that blue need to plus (+) CO2 and Yellow need to minus (-) CO2. Try taking out the tester from the tank it should turn blue after a while.

By the way, you should use water with kH equal to 4 instead of your tank water. There was some discussion on this.

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## EvolutionZ

ohhh.. i did'nt know that! anyway.. why should i use kh equal to 4? that means i need to buy kH test kit? omg...

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## PeterGwee

You need DI or distilled water for mixing the baking soda or just get the standard solution via retailers offshore via the web.

Regards,
Peter Gwee

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## EvolutionZ

hmmm... petergwee.. i don't really understand what you are talking..

anyway.. i'll go get a kH test kit ASAP. so i just use normal tap water.. add some baking soda and test if the kH is 4 then i can use the water for testing my co2 level?

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## PeterGwee

> hmmm... petergwee.. i don't really understand what you are talking..


Then don't bother....

Regards,
Peter Gwee

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## EvolutionZ

> Then don't bother....
> 
> Regards,
> Peter Gwee


oh well, i went searching and found a thread about you and o2bubble argueing about this issue.. i now know what you mean.. will go down c328 to get a kH test kit and buy distilled water as well as baking soda.
thanks :Grin:

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## EvolutionZ

hi guys, went to buy distilled water and API kH test kit today.
my tank's kH turns out to be ~3. so i added little bit of bicarbonated soda and played around with the distilled water till i get kH 4. managed to keep 500ml of kH 4 distilled water.

anyway.. my sera drop checker now is dark green colour. while my co2 is set at 2bps. i think i have to wait for a few hours for the drop checker's colour to stablise?

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## Shadow

I think it will took around 6 hours before it is stabilize.

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## EvolutionZ

> I think it will took around 6 hours before it is stabilize.


okay.. now its turning light green :Opps:  thanks shadow and petergwee for your advice! :Grin:

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