Gar with no appitite

Hello everyone,

About a week and a half ago I saw an add on Kijiji for a variety of "rare" large fish. I went to take a look thinking I might find one or two fish. I was shocked when I went in to his house - the tanks were filthy and smelly, and most over crowded. I came home with 5 Yellow labs, a trio of red belly piranha, a golden colored piranha, a cichlid of unknown type, and a gator gar.

I am looking for a little help with my relatively new gator gar. I am not new to fish keeping and currently have five 80-120 gallon tanks in my home:
Tank 1) 80 gallons - currently houses 8 Yellow labs, a dragon goby, a cichlid of unknown type, a small catfish and a pleco. (Including the new fish)
Tank 2) 80 Gallons - currently houses 3 red belly piranha and the golden piranha (the new group)
Tank 3) 80 gallons - currently houses 1 JD, and 2 large oscars
Tank 4) 100 gallons - currently houses 4 red belly piranha.
Tank 5)120 gallons - currently houses the gator gar

The gator gar is about 14-15 inches in length. He was in a very small (25ish gal tall tank) and it was very murky, dirty, and cold (no heater or working filter). I have set up his tank with large log hides, stones, plants, and natural colored fish rock. He has a good filter, and the temperature is at 26 degrees. I am having problems getting him to eat. The previous owner said he didn't eat for about 2 weeks before I bought him. Since I have owned him he has eaten two small feeder fish, and a pinky mouse. I have left a few feeder fish in with him. I have offered pinky/hopper mice to him and have offered small uncooked shrimp. He wont eat it. Any ideas and tips on getting this guy health and eating would be great!

@FWPrawn - 26c is about 76 or 77F. So the temperatures are correct for him.

@SpatulaKeeper - I will try giving him some bloody bits of steak. Hopefully that will get him eating some more. Ill wait a few days like F1 VET said.

@F1 vet - The golden piranha looks like http://www.aquascapeonline.com/aqua...fish-piranhas-genus-serrasalmus-gold-piranha/ The privious owner had them in one tank together and they seemed to do okay (he still has 12 other redbellies). Do you feel I should separate them? I really like that pothos idea, I will have to try it out in my tanks . thank you for the idea

When you say dont offer any food for a few days, should I take out the feeder fish in the tank or are they fine left in if he wants to eat?

Alot of work? Yes. But I wouldnt have it any other way. I love my fish - got my first redbelly (which I still have) when I was 15. My interest in fish just kept growing and growing, and I am so looking forward to gradually expanding my collection. . Though I already got my dream fish - the alligator gar. Ive been fascinated by them for YEARS.