Sick Oscar! Please Help!

Question
QUESTION: I have a 3 year old Tiger Oscar that I saved from a guy who had her in a ten gallon tank when she was nearly 8 inches long.  I upgraded her tank to a 55 gallon immediately and she has been doing fine until now.  She has lost most of her scales and has changed from a greyish black to a bright yellow color.  She has also been having what look to be seizures!  She shakes uncontrollably for 2-5 seconds.  She has also been laying on the bottom a lot more than usual, and is attacking the back of her tank, which is unusual because she generally takes her frustration out on her tankmate Bakka the Pleco.  Bakka isn't showing any signs of sickness, so I don't think it's contagious, but the behavior is very unusual for her, and I have NEVER seen her turn bright yellow!  Do fish jaundice?!  Does this sound like something I can treat, or am I essentially watching my Mo die?!  Thank you for your time, and I appreciate any help you can offer!  Thank you, Terri and Mo

ANSWER: Hi Terri,
How long has the aquarium been up and running? Is this an established aquarium? If it's a new setup, then it may be due to toxic ammonia and nitrite levels causing the problems. If you've had this setup for a couple of months, it may be an infection/disease.

But, first things first, did her WHOLE body turn yellow? (Like a yellow Tang?) Or are just sections of her body yellow? Of course, depending on the species, or different specimens, Tiger Oscars can have some dark yellow/orange spots on their bodies. Of course, the coloring is normal, if it's only splotches like in the picture in the link below.

See this picture, does your Oscar look like this?
http://www.redorbit.com/modules/reflib/article_images/39_087a64d72d4616cc7031f53

If it looks like that, it's normal.

Check this site for disease diagnosis info:
http://www.fishlore.com/Disease.htm

Since I don't have a picture of Mo, I can't be sure, but see the above link to see if any of the disease profiles fit your Tiger.
Since the Pleco is healthy, I wouldn't bother moving any of the fish, but I would do 20% water changes every day, along with a gravel vacuum. Also, make sure that the water you put in does not contain chlorine or heavy metals. (It's beginner stuff, but just making sure.)

Make sure you are feeding her a varied diet, consisting of a staple food, and a few feedings per week of a live and frozen/freeze dried food. Feeding a variety of foods will put her in optimal health.

I hope she recovers!

---------- FOLLOW-UP ----------

QUESTION: She has been in this tank for a few months, so it is an established habitat.  She doesn't have splotches like the healthy fish in the photo, and she has NEVER had any yellow in her coloring.  Her whole body isn't yellow, it's only in sections, and it's especially dark on her fins and belly, and we have been noticing the subtle color changing for nearly a week, but she regularly "greys out" (which is what the people at Petsmart called it) when she lays eggs, so we didn't become alarmed until we noticed the unusual yellow coloring.  We feed her a varied diet of Oscar Show Pellets, Floating Ciclid Pellets, Brine shrimp, Blood Worms, Beef Heart, and she gets Algae Wafers when she steals them from Bakka.  I knew that I needed to vary her diet, and she is VERY picky about what she will and will not eat, and you have to literally feed her something different everyday or she won't eat!  We treated her water with a dechlorinator, and we will do the water change, but she is also having what look to be seizures.  She shakes uncontrollably for about 2-5 seconds, and she has these a few times an hour!  I'm trying to get all the info I can to you, but I'm very stressed, so I apologize that it's so scattered!  She is also attacking the back of her tank, and swimming in circles, which are highly abnormal for her.  Thank you so much for your quick response!  Terri and Mo

Answer
Hi Terri,
I'm afraid I've never experienced anything like this before in any of the cichlids I've kept. Your diet is perfect, and the yellowing color is quite strange.

I would recommend that you change 30% of the water, and dose with an antibacterial medication, such as Maracyn, as well as an anti-fungal medication. Since the Pleco is not affected, I would remove her from the tank, because the medication would most likely stress her.

I really hope that Mojo, your Oscar, recovers!