I have a Sick Fish, what now?
First, don't panic. Watch your fish for 20 minutes and figure out exaclty what the symptoms are.
Use this site to diagnosis your fish, and find a solution that fits your exact symptoms.
When in doubt, use a hospital tank. Hospital tanks work to isolate your fish, help you diagnosis the problem and if needed allows you to use less medication.
What not to Do!!!
Don't add random chemical treatments to your tank, if you don't know exactly what your fishes problem is you will hurt the fish and make the situation more complicated.
Don't do anything drastic like replace all of the water unless you have a complete die off.
Don't overfeed or feed your fish if they aren't eating while sick. Make sure your fish eat every piece of food you place in the tank during this time or you will soon have an ammonia problem.
To prevent stress or disease follow these recommendations on a regular basis:
Clean Your Fish's Home
For most aquariums, once each week clean the inside of your aquarium with a Magnetic Aquarium Scrubbing Pad. Both sides are magnetic but one side cleans really well. Be sure to wipe down all sides of the tank.
Never use any type of cleaning solution, soap or other products. Also make sure your scrubbing pad is thouroughly rinsed with water before every use.
Clean the Gravel
In an aquarium with a BIO-Wheel the gravel is just ornamental. Fish don't need the gravel, it's purly for looks but acumulates waste product that evenntually turns to ammonia poision.
If your using gravel in your tank, please try to make it as thin as possible. 1/4 inch max. Ungravel filters are outdated, if you have one it might be time to consider a new filter. Use a gravel washer to suck all (alot) of the fish waste from the gravel, this help keep your water quality healthy while leaving beneficial bacteria on the surfaces. Python is a great one to use. Walmart sells them now.
You can avoid lots of fish problems by simply keeping no or a small amount of gravel in your tank.
When in doubt, Change Some Water
Change 20% of the water daily for a week. Make this part of your weekly routine, don't skip weeks. Your fishes health depends on it.
Most tap water is safe to use. If you have a marine tank, obviously this doesn't apply to you. Continually adding new water and removing water will improve your water quality and in turn your fishes health.
Disease & Tank Problems
Common Problems(80% of all problems aquarium issues)
New Tank Syndrome - Is your tank new? Do you have cloudy water?
Ammonia Poisoning - Fins are torn, red steaking on body.
Vitamin Deficiencies - Scoliosis (Curved Spine), Reduced Growth, Lack or Loss of Appetite
Bad Water - Gravel washed this week? Add new water? See Ammonia Poisoning
Swim Bladder Problems - Erratic Swimming Position, Loss of equilibrium.
Physical Injury - From fighting, bumping into things, etc
Stress - Acting weird? Hiding all day? Not eating?
Walmart Syndrome - Did you buy your fish there?
Parasites(Usually visual things/bugs)
Anchor Worms - Tiny white-green or red worms in wounds, Frequent rubbing or "flashing".
Black Spot - Small black speckles on body.
Ich - Small white "salt-like" pimples on fins & body.
Skin / Gill Flukes - Fish gasps for air at the water's surface, gills covered in mucus.
Oodinium (velvet) - Fine grey-gold to whitish 'dust' on the body.
Parasites (External) - Large ugly sores on body.
Planaria - Small White Hairlike Worms in the tank.
Bacterial Diseases(Mostly Internal Problems or invisable problems)
Pop Eye - One or both eyes protrude from the head in an unusual fashion.
Dropsy - Huge, Fat, Bloated Belly, Lethargy and loss of appetite.
Fin Rot - Fins turn Jagged or whitish and die back.
Hole in the Head - Small holes in and around the head.
Fungal(Usualy white foggy type things)
Cataracts - White or grey "foggy" eyes.
Cotton Mouth - White "Cotton like" fungus on the mouth.