Quoted from Rum-Z:
I used to have a planted tank with discus fish and man, I loved that tank and those fish. Discus were beautiful fish that were pretty intelligent (for a fish). But man, the maintenance... I remember having to keep the water relatively soft (acidic) for them as black water with a lot of decaying organic matter is their natural habitat. I'd constantly have to monitor the Ph of the water to ensure that the acidity didn't take a nosedive, which it did a few times leading to panic striken bouts of water adjustments. I had to religiously perform partial water changes and feed them good sometimes live food. You never wanted to deal with "Hole in Head" disease.
Yeah discus are a beautiful fish, probably the best looking freshwater fish / cichlids IMO. But jeez are they fussy with the water!! I also found that they didn't seem as hardy as a lot of other fish either. If things aren't right with most other fish you will notice they are looking a bit sick, have time to adjust the water and put medicine/treatments or whatever is needed then they get better. But the discus seemed to crash really fast! One day they are happy, the next you notice they aren't and shortly after they are dead. Well maybe with a bit of no eating in between while they turn as thin as a wafer - then die!! AND they are a bloody expensive fish here in Oz and it would take ages to track down the different sorts of colours/patterns I wanted on them too.
I thought to keep them again I would need plumbing set up right next to the tank where I could actually have automatic partial water changes occur every couple of days. The room the tank was in probably had too much natural light which meant algae was a pain so I was always having to shave the glass then suck up all of that plus other plant material. It took me a long time to get the tank right to get all the plant growth (plus track down different species of plants), I used to have CO2 injected directly into the tank to help with the growth. Once I got it all set up correctly (CO2, substrate, fertiliser) the plants exploded! Had the tank for years and it looked awesome in the room and people always gravitated to look at it when they came over, but $hit it ultimately was a lot of work.