When your gourami fish hanging from the bottom of the aquarium then its sign to something gone wrong with the fish. Below I listed some point which may help you to understand why your fish hanging from the bottom of the aquarium.
Stress: Stress can make nervous gourami and more likely to hang the bottom of the aquarium. Poor water quality and incorrect water changes can stress most fish.
Disease: Illness may cause your fish bottom to hang from the aquarium. If you look at some unusual things such as spots, bumps and damage then you need to understand that your fish is sick.
Shock: Maybe gouramis are very hardy and easy to care but sudden water and temperature changes can shock them and they move to the bottom of the aquarium.
Hope this short description can make you understand why your fish stay bottom of the aquarium. Take care of your gourami fish and make them happy.