Prevention is the best way to fight any diseases in fish. Good water quality, keeping water conditions appropriate for your angelfish species, and providing quality food will prevent most diseases.
Water Quality
One of the first places to start is water changes. Changing about 20% of the water regularly is a good way to keep good water quality, which helps prevent parasites and diseases in fish by controlling the fish tank cycle. Check the water for quality in between changes. This includes monitoring and adjusting pH, nitrites, nitrates, and hardness to meet the specific needs of your angelfish species and the tank mates. Some fish stores will test water for a nominal fee or for free or you can use aquarium test strips found at any pet retailer.
Don’t Overcrowd the Fish Tank
Not overcrowding the tank is also important. It is preferable to keep the tank under populated at all times rather than overpopulated.
Feeding Angelfish
Also, fish should always be hungry. If they aren’t they may be getting too much food.
Look at each fish when feeding, or at least once a day to examine them for any potential problems. The first order of treatment for a suspected problem is to do a partial water change.
Keep in mind that angelfish are omnivores. They need animal and plant matter in their diet. A common disease for angelfish is hole-in-the-head, which can be prevented by feeding plant matter such as spinach, romaine lettuce, and keeping live plants in the aquarium.
Quarantine New Fish to Prevent Diseases in Establish Fish Tank
It’s advisable to quarantine new fish for a couple of weeks before introducing into the community tank. This tank can be a bare tank with no gravel or accessories other than a heater and filter. A quarantine tank is a good use for a simple sponge filter.