Quoted from Slash:
Here's some pics of the 4" x 2" x 2" tank I had for years. Went through various different stages over time, I started with various regular freshwater fish, before gradually getting rid of those and mainly having discus and then to predominately a planted tank where the fish were secondary to the plants.
Finally sold it as I got sick of the maintenance. I would love to have discus again in a fully planted tank - but maintained by someone else!!!
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.