A clean tank will ensure your fish recovers properly from fin rot and prevent the development of fin rot in the future. Get into the habit of cleaning the tank regularly.  If you have a one gallon tank, you should change the water every three days. A 2.5 gallon tank should be changed every four to five days and a 5 gallon tank should be changed every seven days.  If your tank is uncycled, you should do a 100% water change every time you clean the tank. Wash all the tank accessories and the gravel as well. Add aquarium salt to the water after every cleaning to keep the tank water healthy and monitor the pH of the tank so it is comfortable for your fish. Though it may be tempting to fill your tank with lots of fish, overcrowding can lead to high stress levels and a higher risk of disease for your fish. Make sure your fish are compatible with each other and have more than enough room to swim around and interact in a healthy way.  If you start to notice that certain fish are nipping or biting at each other, this may be a sign that your tank is overcrowded. You may need to remove several fish from the tank or isolate one fish who seems to be acting aggressive towards the other fish. Certain fish are known to be fin nippers, including tiger barbs, serpae tetras, and black widow tetras. Angelfish and catfish can be fin nippers as well as pufferfish and targetfish. If you have any of these fish in your tank, keep an eye on them and separate them from other more vulnerable fish, like guppies. Try to give your fish a varied diet of high quality food and stick to a consistent feeding schedule. Overfeeding and underfeeding your fish can lead to a poor immune system and put your fish at a higher risk of diseases. Giving your fish too much food can also introduce too much bacteria into the tank, as uneaten food will float around in the water and increase the concentration of bacteria in the tank.

How would you rephrase that briefly using Vietnamese?
Giữ cho nước trong bể luôn sạch và thay nước mỗi tuần một lần. Đảm bảo không thả quá nhiều cá trong bể. Cho cá ăn thức ăn chất lượng cao.