Increasing water hardness

[Avel1896]

my soft water fish would thrive in near zero mineral conditions.

There are only few fishes that live in these water conditions. My Betta channoides and brownorum needed this conditions.

 

[Byron]

There are only few fishes that live in these water conditions. My Betta channoides and brownorum needed this conditions.

What about all the fish species in South America, and much of SE Asia? There is basically zero GH and KH in most of the watercourses in the Amazon basin for instance. I think the pH might be more of an issue than GH with some soft water species.

I've kept soft water fish for years, in water with 7 ppm GH (according to the water authority, though I suspect it is less) which is what comes out of my taps. Not RO exactly perhaps, but it contains basically no mineral. I believe @seangee uses pure RO for his soft water tanks, he can confirm.

 

[Avel1896]

I think the pH might be more of an issue than GH with some soft water species.

Usually pH of RO water is around 6.3 and GH KH are 1, then at least regarding my 5 steps RO water system. I used peat then realizing the time needed for peat to establish itself I opted for leaves (catappa, oak) and alder cones.

 

[seangee]

@Byron is correct. 3 of my tanks get pure RO water and minimal fertilasation when I remember. All are low tech and minimal maintenance. I have no interest in breeding but the populations are fairly stable as some fry do survive without intervention. The only exceptions are the cardinal tetras (although the tank is dim there is too much light) and the bristlenose (I only have 1), but he is 17 years old. These are not biotopes but one is full of South American fish, another has all Thai fish and the third is a community of nano fish. Each tank has a different, but stable, pH and all are acidic. The amount of plants, wood and fish are what makes the water go more acidic due to normal biological processes.

pH stabilisation is achieved by 75-80% water changes most weeks. As I am not home every single week they do sometimes go 2 weeks, and rarely 3 without changes. More on the tanks in this fairly old thread. Plants have changed in appearance and distribution as I only trim when it is completely jungle, they are due for a trim soon