I bought a beta fish a week ago and today he seems sick. He is not eating much a...
The most important aspect in fish health is good water quality.
Have you tested your water lately? If not, PetSmart offers free water testing. Bring in a container of your aquarium water today and the PetSmart associates will test it for you to see if you have any toxic ammonia, nitrite or nitrate in the water. You can also pick up free guides on fish diseases and on water quality in the aquarium.
To maintain a healthy environment for fish, you need to change 10% of the water every week in your aquarium, or at least 25% of the water every 4 weeks. Take out the old water and replace it with dechlorinated fresh water. Doing that will keep your water clean and your fish healthy.