First I QT any one showing signs of flukes, and then treat them, Ich is never a problem at my temps. Second although I do not need to do WC I do daily to keep any ecto parasite down to low levels. I also vacuum daily throughly a section of the gravel daily. Vacuuming seems to rid snails and they are a big carrier of flukes. I run a hydroponic system overhead no other need for filtration. All plants are bleached before being added, All cat fish and plecos are keep in QT for 6 months and treated for worms and flukes. No new additions of baby discus until they reach 4 in. but now all my 4 in. are 6+ so the babies are kept in a separate grow out tank until 6in before going into the planted tank. Which means I keep them in QT for a very long time. I will not add tetras, or any cat fish without a six month QT. If there is a sign of flicking that catches my attention I watch that fish for 24 hours and count how many times it flicks. More then twice into QT. The water is treated with prazi for 24 hours every three months. Note I do not let the prazi stay in the tank for recommended treatment time it is just for the free swimming parasites that may have hatched. Pretty much I just do the maintenance and Qting to limit the introduction and to control any living parasites within the tank. So knock on wood I have had little problems. I also do garlic in my tank every two weeks.