by treated you mean declorinated right? Now that we're on the topic, what is the best (least stressfull) wasy to treat the water/ do WC's?
You get a bottle of "Prime" add it to the water acccording to the instuctions.Simple like one capful for every 50 gallons.
Helps to know the age of the Discus you are buying.Like humans stop growing at about 16 years of age the Discus will stop at around 18 months.An Eheim filter is not a good enough reason not to do 2 water changes of 40-50% weekly.If the fish are smaller than 3.5 inches and under a year old you should more to get them to grow and remain healthy.