IMPORTANT - Some strains of Discus fish will Pepper with a dark background or dark aquarium substrate . They will develop tiny dark dots as they try to blend with their darker discus fish tank decoration. Dark discus tank decorations are best avoided if you want to minimize peppering.
Some tanks have no aquarium substrate (gravel or sand on the bottom). These bare bottom tanks can be kept very clean as there are no hiding places for dirt or debris. You may like this look you may not, but it has some advantages. If you prefer a more natural look you will want a substrate. If you want plants you will definitely need a substrate.
Large gravel has lots of gaps for old food and debris to get stuck in so is best avoided. This is never good for water quality. If you want a substrate in your Discus tank sand is the way to go. Any aquarium sand is suitable and there are many colours to choose from.
Rock work looks nice but its not essential. Discus prefer to take cover amongst plants and are not cave dwelling fish. If you like the look add rocks to your discus fish tank decoration but make sure they are suitable for an aquarium.
A quick test is to drop some vinegar on the rock. Any sign of fizzing, its not good for your fish tank.
Wood looks very nice and can benefit a tank. Be sure to purchase from a reputable aquarium supplier and make sure it is the correct sort of wood for your tank. It needs to be soaked before adding and it will turn your water brown as Tannins leach out of the wood over time. This can soften the water and is natural for these fish.
Some species of fish need some bogwood in a tank as they eat it. So for some its a required addition.
TOP TIP - New wood can get a fungus covering when first added. Looks horrendous, some fish will eat it but it will go and isnt harmful.
TOP TIP 2 - Make sure no waste or uneaten food can get stuck in your discus fish tank decoration or aquarium substrate