but why do we change water... if it is for good quality, then how do we judge the quality.. and if it is for good temp. ph. etc. why change it if these are good. also surely you should not overdo the quantity, i would assume we still need good continuity of water.
my fish are kept in tap water, i live in northamptonshire, which i think has just the right hardness/softness etc. for good discus water. i also have excellent plant growth without too much algae, no additives whatsover