New Tiger Oscar

Question

"I recently bought a 55 gallon tank and am keeping a lone tiger oscar in it.  
He's very active, constantly swimming back and forth, up and down, and
jumping towards the lid of the tank.  When i got him a little more than a week
ago he was dark black with orange stripes, very defined.  Now he is almost a
dark green color with less definition in his stripes, also his eyes are beginning
to become cloudy.  Is there something that i can do to help him other than
frequent water changes (which i have already done one of in the week i have
had him)?  Also how much often should i keep his lights on in the tank?"

Answer
Hi Mitchell,
Too much light brings stress to fish, and when fish are stressed they get sick.  I would say that 4 hours of light at night is enough for them.  Try to keep the lights on in a timely manner, meaning that if you put the lights on from 6:00 PM to 10:00PM, try to keep this every day, and not change the hours.  
Vary his diet.  Feed him quality food, a good flake, frozen foods, such as bloodworms, etc.  You should also feed him frozen peas, and vegetables that you cook a little before feeding...also pellets that you presoak before feeding.  Presoak the pellets to make it easier for him to digest.  Oscars need to be well fed.  Never feed them feeder fish as these fish have no nutritional value, and are sometimes full of disease.
Check your water for ammonia.  If you have ammonia in your water, do water changes until you are rid of it, and ammonia is down to zero, or safe.   Ammonia is the number one killer of fish.  Do your water changes every week without fail, and check your water weekly to be sure that your water chemistry is right.  You will find these small test at your Pet Store, and they are a "must have" in your fish cabinet.
When you are sure that your water is free of ammonia treat with medication that you will find at your pet store.  You will find good medication at your Pet Store for Cloudy Eye, and Popeye.  Do not let this situation linger on, as treatment should be made as quickly as possible....but make sure your water chemistry is right before adding medication.
I hope he gets well soon
Lynda