1. Angelfish are normally very peaceful fish, in times of breeding they can get aggressive. It is a good idea to only keep one pair of mating angelfish in the same aquarium, as more of them can lead to infighting.
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. 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.