I had some trouble for a while but when i bought my R.O. system it cleared everything up. i knew I had water problems when I killed a couple of green chromis. My tap water is from a well and is loaded with iron and lime and clacium. some fish such as my yellow tang and my yellow tail damsels had no problem but I killed 5 percula clowns over two years. now that i've completely switched over to R.O. all of my fish are thriving including a percula.