# kH disapears in tank



## brrr (14 Mar 2010)

Hello all

I have a new question wich i willtry to explain in english  

I have a CO2 injection system for my wellplanted tank.
It's secured with e pH detectionsystem, so when the pH is to low, no more CO2 is injected.

now,
the kH in the tank(carbonate hardness) is nearly 0. wich brings the pH around 6.10
this is ofc under te minimum limit for pH injection. so to CO2 concentration is very low, wich
ain't good with that many plants in the tank.

now the question:

the water i use to clean the tank has a kH of 4-5, wich is perfect.
when I raizes the kH of the tank to 4.5, i thought i could maintain that lvl of KH with refeshing 15% every week
with fresh water with 4-5kH aswell

but somehow, the kH drops to nearly 0.

howcomes?
what sucks this away?

I have some wood in it, JBL filter, no uv or other devices.

plants and fish... no stones, juist one porous (i hope this is a good translation lol) thingy in stone.

anyone got any idea?

thanks in advance
grtz
Bert


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## JamesC (14 Mar 2010)

Hi Bert,
Great to see someone from Belgium. I spent 12 years of my young life living in Brussels. Anyway what substrate are you using? Clay substrates often lower the KH of tanks but over time this does slow down and stop. Wood can also lower KH but not that quickly.

James


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## brrr (14 Mar 2010)

Hi James

How cool you lived in Brussels. did u speak english, french or Dutch?  

well, what do you mean with substrate?
in the filter or as bottom?

the bottom of the tank is just sand...

in the filter i use the blue filter medium and stuff with a lot of surface for bacteria, nothing else.

the kH realy drops from 5 to 2-3 within 1.5 week...
so quite fast.

I realy don't like to use chemics in my tank, so I hope i can eliminate whatever is causing it.

ow yea I do use profito every week,
but I don' tthink that will take the kH away

grtz
Bert


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## JamesC (14 Mar 2010)

I lived in Waterloo and went to the British School Of Brussels in Tervuren. So mainly spoke English but also learnt French fairly well.
Do you have much wood in your tank? Can't think of anything else unless you are adding phosphate buffers.

James


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## brrr (14 Mar 2010)

Waterloo, the famous city if you know your history lessons  

you say phosphate?

I study labrotory so if u can tell me how that inflicts kH I will understand it.

I must say the phosphate lvl is going out the roof.
never realy tried to ge tit lower as it wasn't causing any problems...

but if u think that it does inflict my kH lvl, well then I will lower it to more apropriate lvls
(by using the stuff made for JBL filters, would that be a good way???)

don' thave that much wood actually
1 big piece and one smaller...

still learning
great how much u guys know


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## brrr (15 Mar 2010)

so just so I keep learning,

how does phosphate inflict kH?


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## JamesC (15 Mar 2010)

KH test kits don't measure carbonate hardness but instead alkalinity. This thread explains a lot more about it - http://www.ukaps.org/forum/viewtopic.php?f=51&t=4869. Therefore if you add a buffer then the alkalinity that your KH test kit measures will change. pH up buffers are normally HCO3 based and pH down buffers are quite often phosphate based.

Not saying that this is what is causing your pH drop but can't see what else it could be at the moment.

Loved living in Waterloo and am still very partial to some moules frites.

James


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## Graeme Edwards (15 Mar 2010)

Check there isn't anything steal i.e normal, non stainless steal, that has fallen in the tank. Ive had the same problem. It turned out to be a lost razor blade. Once the razor was removed, things started creeping back to normal. 

Im not sure how this worked, or if its a coincidence, but it did seem to be the trigger.

Cheers.


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## Mark Evans (15 Mar 2010)

I know nothing about the science bit, but my nano has no KH and is the high 5-low 6 PH and i've not suffered at all.

fish are happy and plants are gorgeous.


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