# Other Aquarium Forums > Fish Care, Nutrition and Water Management >  Ph & Kh

## stanley

Hi,

I just got the JBL Ph &amp; Kh testkit and this is my tank results :

Ph 5.5 
Kh 4 - 5 degree 

I put 4 - 5 drops then the colour changes from clear to yellow-orange, I dunno really how to see the colour changes.. can someone pls help me on how to do the Kh test and what does it means ?


It a 2ft planted tank tank with DIY CO2

Questions :

Is the Ph too low in my tank?? I tested the tap water...Ph around 7-7.5

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## David

hi stanley 

test your tank water again...cos if your KH is at 4 to 5, you should have seen a blue solution before the yellow....rinse the valve and dry it will. ensure that there is only 5ml of water (make sure that the lowest point of the water is at 5ml..as water in any cylinder will create a U-shape). shake the solution well....and drop...count the number of drops and the total will be the KH reading.

Is your fishes gasping at the surface? They should be by now coz at KH 4 to 5, the 'correct' PH for CO2 rich water should be around 6.5 ot 6.6...at 5.5 you have way over injected CO2....Should you PH be correct at 5.5, than you KH will be at 1 or near 0.

If your fishes are gasping at the surface execute a 50% water change and stop CO2 injection. If your KH is at 1 or near 0.....add baking soda or KH up powder to increase KH level...never raise the KH by more than 2points within 24hrs.....suggest is that add 2 teaspoon at a time...dissolve it well and pour it evenly round the tank...wait an hour and take the reading again.....continue the process till you reach your 24hr quota.....ideal KH level should be 4 to 5.

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## stanley

David,

Thanks for the prompt reply... :Smile:  

My fish are doing fine mostly neon tetras, not gasping for air in the surface at all

When doing the tests, I actually drop like around 7-8 drops but still no changes... the water just turns more yellow-orange due to the orange drops... so I was kinda wondering if I did the test correctly...

What is the Kh for tap water.. perhaps I'll try them on the tap water first to see is there any blue before yellow...

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## juggler

Stanley:

I think your kH is 0. Tap water is usually 0 dkH or at most 2 dkH.

If your sample tank water has some carbonate hardness, the first drop of kH solution will turn the water blue. You keep adding drops until it turns yellow. The number of drops will determine the dkH.

As a test, you can add some baking soda to a sample of tap water. Then test the kH. It should turn blue at the first drop.

Having 0 kh is not good as the pH can be quite low due to CO2 fertilisation and therefore harmful for fish.

You can get some kH powder from LFS to increase the kH. But increase the kH slowly. In my case, my tank has some coral sand and it contributed to about at least 5 dkH.

After increasing the kH, your pH should stabilise towards 7.

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## sherchoo

agree with juggler. raise your kH but please do it gradually. 2deg in 24hrs is ok but I recomend 1 deg a day.

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## loupgarou

I just got a kh kit as well, for a planted tank, waht should the values be?

I think my ph is 7.0 - 7.4 (can't tell).

my kh is 8

co2 is being pumped it but the plants arent' bubbling, so I suspect the kh is too high (cos i'm using MH lights).

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## Simon

> ----------------
> On 1/11/2002 11:51:51 AM 
> 
> I just got a kh kit as well, for a planted tank, waht should the values be?
> 
> I think my ph is 7.0 - 7.4 (can't tell).
> 
> my kh is 8
> 
> ...


u gotta confirm the reading for yr PH.. .4 difference is alot.. at PH 7, yr KH shld be ard 6-7 (i think)

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## daniel

Hi

I'm new to this
May I know what is KH and how will affect the PH and what is it suppose to do.
I know that the more CO2 u pump the lower the PH.
Thx

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## stanley

Hi,

Wow, I just added 1/2 teaspoon of baking soda into my 2ft tank... within 10mins..all the plants starts to bubble..  :Smile:  


Plants are :

cabomba - a little bit only, mostly covered by algae.. [:0] 
java fern - a lot on the leaves
Egeria Densa - a lot of bubbles
java moss - a little little bit

Tested the Kh... 1 drop, light blue... 2nd drop..no colour...3rd drop
yellowish.. so the Kh is 3 right??

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## benetay

Yup thts correct KH 3 very low. increase KH.

Test yr KH again after u put Baking soda.

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## DEA

> ----------------
> On 1/11/2002 2:46:00 PM 
> 
> Hi
> 
> I'm new to this
> May I know what is KH and how will affect the PH and what is it suppose to do.
> I know that the more CO2 u pump the lower the PH.
> Thx
> ----------------


kh is carbonate hardness, a measure of how much carbonate there is in your water
in practice, we think of it as bicarbonate

when you inject co2, a buffer system is setup between the carbonic acid and the bicarbonate
in simple terms, if you inject too much co2, the bicarbonate cannot buffer the H+, the pH will skydive

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## David

Malaysian

KH or carbonate hardness acts as a buffer for dissolved CO2......

A rough guide for CO2 rich water are

KH 3 = 6.3
KH 4 = 6.5
KH 5 = 6.7
KH 6 = 6.9

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## vinz

> ----------------
> On 1/12/2002 1:28:05 AM 
> 
> Malaysian
> 
> KH or carbonate hardness acts as a buffer for dissolved CO2......
> 
> A rough guide for CO2 rich water are
> 
> ...


Errr, David. What are the numbers on right side? pH?

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## vinz

Any difference between baking soda and KH up powder in terms of effects on the tank water?

Is it cheaper to use baking soda? Any reason to use KH up instead of baking soda?

Thanks.

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## Simon

yes, vinz those numbers represent PH.. u can use baking soda instead if u find KH up abit ex

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## williamng

Wat KH you guys recommend. I read books and they say 3 - 4 is good.

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## Simon

william, depending on yr PH level.. KH co-exist with PH.. see the image below



a KH of 3-4 will give u a PH of less than 6.7

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## stanley

Hi,

I just added another teaspoon of baking soda ( total 2 teaspoon in 2 days ) and my ph &amp; kh changes is as follows :

KH, from 3 raise to 4
PH, from 5.5 ( before adding baking soda ) to 7

But now my plants isn't bubbling at all.... is this because of the raise in Ph and therefore a drop in CO2 in the water ??

From Simon's chart, that is what it is saying....... should I increase my Kh even more ??

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## Simon

best if u can test the water again.. then raise the KH to at least 5-6 and PH at 6.8

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## David

hi william

that correct...between 3 to 5KH level is good for plants....but I know some do push it to 6 to 7 with good results.

hi stanley

you are right....when you increase your KH level, the correct PH level for CO2 rich water changes....when you KH is at 4, PH at 7...it means that there is issufficient dissolved CO2 for your plants..the correct PH level for KH of 4 should be landing around 6.5, 6.6...do not increase you KH level anymore...you should be injecting CO2 till your PH reaches the desired level.

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## DEA

by right
bubbling should have NOTHING to do with your kh
nor does kh affect the co2 in the water
think of kh as fixed, and pH then dependent on the co2 you're injecting

however
1 theory for why you see bubbling immediately after the addition of baking soda
plants can and do take in bicarbonate directly from the water
the plants suck it up and photosynthesis quickly
so quickly in fact they exhaust the other nutrients in the water which they need

try adding some fertiliser to your tank
and see what happens

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## jacian

> ----------------
> On 1/12/2002 11:52:22 PM 
> 
> Any difference between baking soda and KH up powder in terms of effects on the tank water?
> 
> Is it cheaper to use baking soda? Any reason to use KH up instead of baking soda?
> 
> Thanks.
> ----------------


Baking Soda is Sodium Bicarbonate, not sure what is in KH up powder.

KH up costs abt $7.00 for 150g while baking soda costs abt $1 per 100g. If you buy from Phoon Huat, can get 500g for abt $3 (can't remember).

If KH up powder is Potassium Bicarbonate, I may consider using it else Baking Soda would do the job.

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## vinz

What does it take to maintain the KH once its up? Does it take regular dosing or just replace according to water volume changed? Just want to know what it takes before I start.

Any guidelines for the amount of baking soda to use per volume of water per points raise desired?

Anything else to watch out for besides no more then 2 points raise per 24hrs?

Thanks.

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## jacian

It takes about 2g of baking soda to increase kH of 60 litres water by 1 degree.

Generally, with CO2 injection, you only need to replace according to the water changes. In cases where CO2 is limited, some plants are capable of using the carbon from the carbonate. This will cause the kh to drop.

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## daniel

David

Does that mean I do not need to check PH 
if I know what is the KH?

Thxs

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## Simon

malaysian, u need to know yr both PH &amp; KH... they r both linked together

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## daniel

> ----------------
> On 1/12/2002 1:28:05 AM 
> 
> Malaysian
> 
> KH or carbonate hardness acts as a buffer for dissolved CO2......
> 
> A rough guide for CO2 rich water are
> 
> ...


David 

Does that mean that I do not need to check PH if I know what the KH is?

Thx

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## daniel

Simon
noted
Thks for the prompt reply

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## David

hi Malaysian

sorry i missed your question.... :Sad:  

hey you a penang person?....errh which part georgetown, julutong, or gulugor...me from gulugor side towards greenlane.

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