# KH question



## Marc1t (27 Apr 2015)

I'm really no expert on water chemistry (or anything really) but I was a bit concerned when I measured my planted aquarium water KH for the first time @ 2 German degrees using a JBL test kit. Most people quote 4to5 being optimal my PH has always remained a rock steady 7 I have a school of Cardinal tetras which seem to love the conditions, all other perimeters 0,  & im not injecting Co2
 I do a 25% 50/50 tap/RO water change weekly this mix has a KH of 5 & my tap water is 12.
Should I worry about this or change anything?


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## BigTom (27 Apr 2015)

Marc1t said:


> Should I worry about this or change anything?



No.


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## Jose (28 Apr 2015)

You can guess a number and make it the kh of your tank. This will be just as useful as a test kit.


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## Marc1t (28 Apr 2015)

Jose said:


> You can guess a number and make it the kh of your tank. This will be just as useful as a test kit.


Not exactly sure what your point is?


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## Jose (28 Apr 2015)

KH test kits are useless. Except more proffesional ones like maybe lamotte ones. So nothing you can buy for £10 is worth it really.


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## dw1305 (30 Apr 2015)

Hi all, 





Marc1t said:


> Most people quote 4to5 being optimal my PH has always remained a rock steady 7 I have a school of Cardinal tetras which seem to love the conditions, all other perimeters 0, & im not injecting Co2. I do a 25% 50/50 tap/RO water change weekly this mix has a KH of 5 & my tap water is 12. Should I worry about this or change anything?


 I agree with the others, it sounds fine. 

The main thing is that  your fish are doing well. Cardinal Tetra are a "black-water" fish, so they come from water with virtually no carbonate hardness, where pH will be below pH7, but might vary form pH4 to pH7 over very short time periods. In very soft water pH will never be stable, because very small changes in water chemistry cause large changes in pH. 

Have a look at <"A Contribution to the Chemical Characterization of Rivers in the Rio Negro Basin, Brazil"> & <"Looking to lower pH">.

In terms of water testing I'd take a different approach. In spite of what you will read on other forums it is really difficult to get meaningful water values for all sorts of parameters (like NO3- etc.) and even if the you do get "ball-park" values often (like pH) they need some interpretation. 

The approach I take is just to monitor the conductivity. It is a measure of all salts (as ions) so it isn't the most useful parameter, but it is the only measure where you can just dip the meter in and get an accurate reading.

When the tank is running well, and the plants and fish look good, you take a conductivity reading, then every few days as you changes water etc take some more readings. This will give you a range of values. 

For soft water tanks I aim for 60 - 120 microS (~40 - 80ppm TDS), and I just change the proportion of  tap (about 17dKH, and good quality) and rain water (RO for you) during water changes to maintain this range.

I use the <"Duckweed Index"> to feed the plants on demand.

cheers Darrel


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