I have set up a new Planted 4ft Discus yank 2 months ago, 6 x Discus added 2 weeks ago after the tank had cycled. It also has 7 x Cory Julii and a few Cardinal Tetras. The tank is approx 220 litres with a separate 30 litre sump. I made a 40 litre water change after the 1st week but the fish were not happy, all sitting at bottom of tank but then the following morning they were ok. I purchased fish from Nick at Sydney Discus World who appears to be very knowledgeable and was told NOT to make any further water changes for at least another 2 weeks and then to only change no more than 10% water weekly, preferrably fortnightly. I do not want to do anything to harm these fish and I am confused, hearing so many stories of people who change up to 50% water weekly which also seems excessive. Today 1 of my fish is only breathing from 1 gill at a time. Can this be due to water conditions?
Can anybody help?.