I've experienced this before. I had a tank of tropical fish that were all thriving, but when the weather got colder, the fish started dying one by one. That's when I realized that tropical fish can't tolerate cold and need heating equipment.
Most tropical fish thrive in water temperatures between 20 and 24°C. The tank can be placed in a sunny room, or controlled by a stove, heated floor, radiator, or electric heater. Electric heaters should ideally be equipped with a thermostat, and the power should be turned off before placing the fish in or removing it. Simultaneously, the dissolved oxygen level in the water should be adjusted. Artificial temperature control primarily utilizes heating methods such as stoves, heated floors, and radiators. In recent years, electric heating appliances have become increasingly popular and represent a better heating method. Most electric appliances have automatic temperature control functions, and these should be the preferred choice.
Besides aquariums and water filters, equipment for keeping tropical fish includes water circulation and filtration systems, heating systems, aeration systems, lighting systems, and pumping systems. For a single aquarium, a small circulating filter pump, a 100-200W heater, single- or double-hole air pumps, fluorescent lights, and small submersible pumps are suitable. Aeration equipment is also necessary; options for tropical fish include single-hole, double-hole, and four-hole air pumps, as well as turbine-type aerators.For a single aquarium, a single-hole air pump can be used. For multiple aquariums, a double-hole or four-hole air pump can be used. Single-hole, double-hole, and four-hole air pumps are all made of plastic and use the movement of a rubber stopper to aerate the water. After prolonged use, the rubber stopper may crack or age, at which point it should be replaced promptly.
The most important thing in keeping tropical fish is controlling the water temperature. In summer, whether the heater is on or off doesn't make much difference, but if the temperature drops, the heater must be turned on, otherwise the tropical fish may freeze to death.
