My Pleco won't eat and seems ill (sob)

I don't know what happened. I looked at my 7 inch common pleco two days ago and I could tell something was wrong. He has a few torn fins (this happened once before because he got stuck in a cave - but I removed that) and he has not eaten since. He is normally a huge pig when it comes to feeding time. He has been on the bottom of the tank barely moving 8( I'm so sad. He's our favorite. I have been keeping his water extra clean. I have tried tempting him with goodies but he won't eat. I even put some squash in there from the garden.

The tank is a 90 gallon with live plants and driftwood. No ammonia, no nitrites, no nitrates (ever, is that normal?), ph is about 7.2, temp is 77. I change 30% of the water once a week and gravel vac, could that be why there are no nitrates? He shares the tank with a striped raphael, 2 ADF's, and a few clown loaches and guppies. I know they will need a larger tank at some point, that will be no problem so don't worry 8)

Heres a photo of him at the bottom of the tank where he been very lethargic, you can see his ripped fin also, sorry for the bad pic.........Is there anything I can do for him other than keep his water super clean? 8( Michelle

Thanks. I put him in a QT tank and used Maracyn for three days but had to put him back in the main tank when the antibiotics caused water problems. He seems a little better. I have seen him eat a small amount. He went longer than a week refusing food so I am happy to see him eating even a little. I am still watching to see if the fins are getting better. Hard to say at this point.

He's like a puppy dog to the family. I saw a huge 18 inch pleco at the LFS today and I thought to myself, that maybe one day ours can grow that big too 8)

Thanks Pete!

Thanks guys. I will try your suggestions and hopefully post a happy update soon. I'm keeping a close eye on his fins, I would like to see more improvement by now. I am keeping his water super clean and keeping my fingers crossed.

Interesting about the nitrates. I used to have low nitrates before I went to live plants so that makes sense.

I have good news......my beloved pleco seems to have improved. He is back to hanging on the glass instead of looking dead on the bottom of the tank and being pushed around by the current. He has been eating better and this morning was the first day I noticed definite improvement of his fin rot, the gaps are filling in. I must go know on wood now..............

Thanks for all of your help!