somethings not right??

Hey all i am new to the forms just signed up about 20 min or so ago. I was trying to find the introductions thread but cant seem to do so. Anyway I am glad i found this forum and i am hoping that someone can help me. My husband and I have 133 gallon fish tank which has a few different fish in it the one i am worried about is our saddle bichir. Looks fine on the outside but there is something not right with him on the inside. He lays upside down a lot. be doing this for oohhh i don't know maybe 6 months or so now. very rarely is he upset right. He is still swimming around from time to time and going up to the surface to get air. I don't think he has eaten in maybe a week now . I was looking though the forms a bit before i made this post and noticed that they become over fed very easily . I am wondering if this is what happen? we only fed him once every night.

Please let me know what everyone thinks. if you need more info on my setup or a picture or to ai will do my best to get some for you.

Thanks

here are a couple pictures of him

it has been awhile now not sure on the time frame. he was not like this when we got him. he use to sit up right. then one day we noticed him upside right but it looked like he had a curve in his body or spin? now i don't notice that anymore. he just looks like one tick log now and lay upside down. He has not eaten for like a week i would say because he smells the food but can get himself around right to eat it .

there have been no changes to that tank or tank mates. everyone else in the tank is fine. I have never fed him frozen prawn tried but he never took to it. he eats pieces of frozen tilapia right now. he used to eat omega one freshwater carnivore formula but the one place i could buy it from closed down is there anything else i could try and fed him.