Agg's Discus Guide
I am an experienced aquarist who has recently begun keeping Discus fish. I found when doing my research that there is a LOT of information available, but much of it is conflicting. Also, a lot of the accepted knowledge about keeping Discus seems to be persisting from decades ago when Discus were mostly wild caught and a lot more fragile than those available now, most of which are bred in captivity. So, the purpose of this page is to record the knowledge I have collected before I forget it all, and to detail how my real-world experiences match or conflict with that information. As mentioned earlier I am very new to Discus keeping (but have been fishkeeping for nearly 15 years) so my experiences may not be correct for you. But I hope you find this guide useful. Good luck and enjoy your fish!
Discus are unusual in that they are very slow feeders. For most tropical fish many people recommend only offering as much food as can be eaten in two minutes, or five minutes, etc. This will not work with Discus as they prefer to graze and pick food from the bottom of the tank, often for more than an hour after feeding. You don't really get the thrashing feeding frenzy at the surface that you see with rainbowfish, angels and most other tropical fish. You should really feed them at least twice a day, although like any fish one or two days with less food or even no food is not going to harm them, and simulates the natural environment where there are sometimes food shortages. Even if you don't feed them, they will find things to peck at in the tank.
If you look at the "face" of a Discus, they have a very small mouth for their size, and a large brow leading up to the dorsal fin. Because of this they have difficulty feeding from the surface of a tank. Compare for example with a rainbowfish which is excellent at picking food from the surface such as insects which fall into a stream. The rainbowfish has a large mouth positioned well out in front and a sleek torpedo-like body, so has no issues hitting a surface object at speed. Discus often seem baffled by food at the surface, blowing water at it to try and break the surface tension to make it drop. Some of my discus will peck at a pellet sitting on the surface, and very rarely even try for a piece of tropical flake, but in most cases they wait until the food starts to sink. Even then it can be too fast-moving for them and they simply follow it down to the tank floor, then peck at it there. It's also a good idea to turn off your tank filters when feeding, because firstly it trains your fish to come to the front/surface when the filters are turned off, and secondly it means they don't get food being blasted past them and unable to reach it.
Discus require a high-protein diet. In the wild they pick worms and crustaceans from the substrate. The staple diet of captive Discus seems to be frozen blood worms, and that's certainly true of mine. I give them one or two blocks of frozen worms with every feed. However I also offer them pellet food, as well as flake, frozen brine shrimp, frozen beef heart mix, etc. Any quality tropical fish food should be fine and it's good to vary the diet of any fish, but Discus definitely prefer frozen once-live food. BTW, brine shrimp don't really contain much protein or actual nutrition, but they provide roughage which is good for the digestion.
Live food is generally a bad idea for fish tanks of any kind. If you have a specialised fish like Piranha which will only eat live moving things, then fair enough, if you can handle the cruelty side of it. But be aware living food brings with it the potential for parasites and disease. Even if you trust your source of live food, do you trust their source? I have fed my fish live red worms from my own worm farms, the commercial bin kind which you feed food scraps to, and they have been well recieved. But even though I control everything the worms eat, I'm not really comfortable with introducing live creatures, plus whatever is stuck to them or living inside them, to my carefully-managed aquarium environment. Of course, poor quality frozen food could have the same issues but it's far less likely due to having been frozen for so long.
I put the tankmates section below the feeding section because one of the main issues with keeping Discus in a community tank is their poor ability to compete for food. Sharks or rainbowfish or any other fast-moving aggressive feeder is going to beat Discus to the food every time, as well as frighten and buffet them around. As mentioned earlier Discus prefer to pick food from the tank floor, and I know for example in my rainbowfish tank virtually no food makes it to the floor, never mind sits there waiting for a Discus to eat it. I've seen rainbows hit a block of frozen brine shrimp from underneath, hard enough to fire the block out of the tank and across the room, and launch the fish out of the tank onto the glass lids. Discus will not cope in that kind of environment, you will never see them and they will not get enough food.