The Icelandic water is very good, pH around 8.0 and no nitrates, I do 30-40% water changes every 10-18 days and 50% every 2 days in fry tanks. The fish grow like weed and are very healthy. I have never had any disese in my Mbuna tanks.
Tanks are well filtered, most of them with Rena xp3, I only clean the Xp3 every 4-6 months.
Plants are mostly Valesneria Gigante and Anubias.