Thanks bro,like I was not in town for past three days,before leaving I added 1tsp Rock salt in the tank,today when I came back FH was very dark almost black body and deep red..I replaced 25% water with fresh tap water..and now colour has lightened..Is it becoz of salt?And regarding water changes many recommend 25% to 45% weekly once.My problem is my tap water is very hard contains lots of minerals..sediments like calcium, after 3-5 days it becomes clear,No cloudiness..Each time my filter is full of sediments..Can I change water once in a month?What do you think?