My Flowerhorn is severely sick and about to die, HELP ME WHAT DO I DO!

Question
Hi I have a flowerhorn fish who is about 5-6 in big in a 120 gal aquarium we've had her for about a year she has been doing fine until the a yesterday when i woke up and saw her frantically hump up as hard as she can and hit the lid of the aquarium and the wall as if she had a seizure and then lay down on her side at the bottom of the aquarium she has been laying down on her side for two days now she tried to swim once but she sinks down shes still breathing and moving her gills even thou today she was breathing really hard she also preiodically jumps frantically as if shes having a seizure and hits the lits and the wall like before and just sinks back down and today she started on and off loosing her color and turning white and her eye truned from black to red and then she comes bak to normal color and does it again....I do not what to I just changed the water too I'm so worried I brought the fish as a birthday gift to my wife and she has become a part of our family and we're all devastated especially because she is so beautiful I'm willing to do anything and really hope its not too late please tell me what I can do !

Answer
Hi Michelle:  I am sorry to hear that your flowerhorn is ill.  I would begin by cleaning the tank extremely well...including the gravel. What you have described to me sounds like poisoning.... Do you know what your water chemistry values are?  has your pH dropped suddenly? or risen?  I think you should also check your heater and make sure there is no water inside as a small crack could cause her to leap from electrocution.  Ammonia/nitrate/nitrite poisoning is another possibility.  a partial water change would help to cure that.... but the heater is my biggest concern...if it is broken take it out... replace with a new one... if you can look at these items and get back to me we can try to diagnose what is wrong with your fish... dave