Is 13 Gallons too small for Discus fish?
Far far far too small. Discus are fish that can get to the size of a dinner plate and need immaculate, ridiculously immaculate, water chemistry. Some locally bred fish may be hardier to water chemistry than others though. To keep Discus you need a minimum of a 55 gallon, preferably large, which is extremely well cycled and several months mature with a set up to ensure stable acidic water chemistry, ideally a pH around 6. Discus keepers use things like peat filtration to achieve this. They also need their water very warm, around 82F up to 86! Basically Discus need a tank designed specifically to their needs, and yes they work in planted tanks, there are other fish that can tolerate such conditions, but they should be secondary to the Discus. Also, Discus are, at the end of the day, Cichlids. I know my friend had a group of 6 juvenile Discus, think he’s now down to 3 healthy older juveniles which killed off the other less-dominant bottom-of-the-rung smaller Discus!
