The aquarium owner is also a caretaker of aquatic creatures who must ensure the safety and comfort of the fish every day. There are several rules that an aquarist must follow to keep their fish in excellent condition. One of them is the need to isolate fish when they are breeding, suspected to be ill, aggressive, or just acclimating to the tank. For this purpose, they should be placed in a special compartment called a breeding box. The breeding box for fish, when placed inside the aquarium, is usually mounted with suckers to the glass of the tank. If we are keeping a lot of fish, it is worth choosing breeding boxes that have several separate chambers so that we can isolate multiple individuals at the same time. If we do not have much space in the aquarium, in cases where we do not need to isolate fish, we can store the breeding box for the fish. The mesh breeding box takes up very little space when folded and is perfect for storing fry. The youngest fish must be isolated until they reach about 1.5 cm in length before they can be introduced to adult fish. Otherwise, they may not cope in the "adult" tank, which is why it is so important that their growth period is spent in a safe breeding box.