1. You should always research the different types of fish you are going to be housing together. Certain fish can be extremely aggressive and cannot be paired with other fish of different temperaments.
2. Cloudy water is normally a sign of overfeeding your aquarium. Judge the right amount of food to place in the aquarium to not leave too much residue due to overfeeding.
3. It is a good idea to perform a frequent water change and cleaning schedule. Changing the water in your aquarium will keep it clean for the fish that live in the aquarium. Keep a full stock of the water treatment chemicals you will need for this purpose.