How to handle a huge KH

[Neonus]

Good point.
The problem is that I have only water with GH between 0 and 16. I don't understand what TDS means, never heard about this.

 

[KarlTh]

Total Dissolved Solids. Water softeners work by replacing each Ca++ or Mg++ ion with two Na+ ions - that's why they use salt to recharge. Consequently although the GH (which measures the concentration of the first two ions) drops, the TDS actually rises. TDS is at least as important to fish as the hardness; possibly moreso. A GH of 16 is not a problem unless you're thinking of breeding something like discus or Apistos. It'll be fine for the vast majority of plants (paging Plantbrain... paging Plantbrain... Come in Plantbrain...) and you'll not have to dose calcium...

 

[Neonus]

My intention is to have an easy tank without anything fancy and pretentious. I would like in from of the tank some plants like grass and in the back something bigger. About fishes: something with nice color and not so big.

I don't like goldfish, anyway.

I'm still confused what water to chose, really.

 

[KarlTh]

The unsoftened water. Your water is not immensely hard anyway; the KH and GH are both half what I've kept a wide range of fish in. That water is the best for fish and plants.