Increasing the hardness of R/O water for Central American fish
How would you increase the hardness of R/O water for fish from Central America?
I recommend increasing the hardness with sera mineral salt to approximately 6 - 8 °dKH and, accordingly, approximately 13 - 17 °dGH, unless the fish originate from water unusually soft for Central America. Considering the question, I mainly think of Livebearers, Goodeids and Cichlids from the former collective genus "Cichlasoma", which do well in medium hard and neutral to slightly alkaline water.
Dr. Bodo Schnell