1. Only use medication in your aquarium when you are out of other options. You should use a separate tank to medicate sick fish as some medications can have harmful effects on healthy fish.
2. You should always thoroughly research the type of aquarium you are going to be setting up before you purchase it. Make sure you have the proper gallon capacity and shape that will fit in your home.
3. You should keep the temperature in your aquarium constant. Constant change in the aquarium can be dangerous for the fish in your aquarium. Keep a quality heater and accurate thermometer to ensure that the water stays stable for the aquarium.