New Tank.... Water hardness questions

[zzzzzxx]

I just set up my 30 g aquarium, turned on my filter and heater and so far so good.. I had a few questions about hardness levels. GH is general hardness which is what you look at when deciding what fish to buy? Example: Tetras prefer a water level of 4-6 dH ...that is the general hardness level they prefer?

Then there is the alkaline level or Kh...this works with the pH of the water..the higher the Kh level the more stable the pH of the water will be? What is a normal kH level to have?

WHich is more important..Kh or gh?

any help would be great

 

[Sati]

I'd like to know as well. I've never tested my gH or kH.

 

[Sinuhe]

Yes, when they recommend certain hardness levels for fish, I think it mean general hardness.

The "normal" carbonate hardness depends on the GH level, too, and what you want it to be. KH can't be higher than GH, so in a tank with a GH of 6 dH KH is most probably lower than in a tank GH of 15 dH.

 

[AJ]

They're both important. Certain fish handle certain water types better, there is no right answer. Some like tetras like very soft water, others like cichlids like harder water (I am referring to GH here).
KH like you said is important in terms of pH. If it is too low, the pH in your tank will swing around and cause fish to die. On the other hand if it is too high you will not be able to adjust your pH. Usually if you have a high kH your pH will be high too. Again, fish like platies or cichlid prefer this water.
It really all depends on what fish you want.
Seriously, alot of fish can live outside their parameters as long as they remain STABLE. Which means ensuring KH isn't too low.
My advice - buy a water test kit at your LFS, it will tell you what your water is so you can choose your fish appropriately (if you wish) and will give you hardness numbers that are acceptable and unacceptable.
(I'd give you numbers but I am in Canada and the units would be different making the numbers useless to you).

 

[Sati]

Thank you for the explanation. I'll pick up a test kit at the lfs sale this weekend :]

 

[xander]

So if a fish prefers soft water. How soft is soft. I found the tank I would like to be soft around 4 both KH and GH. I can't imagine that you would want a hardness of 0 or 1 or whatever. I am curious because the tank reads a high ph at 7.5.