Just keep a few tropical fish. It depends on the species of fish and the size of the aquarium. Generally speaking, small tropical fish, such as guppies, zebrafish and lamprey, are raised. It requires a large number to watch in groups. If the fish tank is big enough, it will be beautiful to raise dozens. If it is a large tropical fish, such as arowana, warships, catfish and so on. It is generally good to raise odd numbers because odd numbers belong to yang and even numbers belong to yin. In geomantic omen, 16 is water, and 49 is gold, which is the most prosperous raw water. If you want to analyze it in detail, it will be much more complicated, depending on the location of the fish tank, the variety and color of the fish and so on.
For reference only.