Very hardy fish! I raised one to 18" then donated it to a LFS who put it in a pond after I couldn't house it any longer.
When small(I aquired it at 3") I fed frozen krill, brineshrimp, bloodworms, and chunks of a homeade mixture consisting of peeled shrimp and daily special fish filets from my grocery store blended, compressed in zip-lock bags and frozen.
When it got larger(6") I started feeding nightcrawlers, whole shrimp, above fish mixture, krill, giant danios, and occasionally beefheart.
I don't know if it has any tankmates, but I often had a hard time getting food down to my TSN before the cichlids I was raising him with would eat it. My solution was to take a 36" piece of clear plastic lift tube like you use with an undergravel filter, place the food inside, put it in front of the cats face, and let it float down right to it's mouth. It was almost comical watching the other fish hit the clear tube trying to get the food. After awhile the cichlids learned the chow was unatainable, and the cat would start pacing the tank as soon as I put it into the water. For cleaning I would just run it through the dish washer.
You have a monster on your hands my friend, I hope you have a plan to house it in the future. When I got mine I was told it would only grow to 12". I should have done more research! A full grown TSN can be 48" long and weigh 65 pounds. I had mine in a 125 G. before getting rid of it. It would get spooked and smash the glass soo hard it's nose went from being beautifully flat, to permanently bent. It would wake me up at night sometimes from bashing the tank. I would check on it and it's face would be bleeding. Not good. Also broke about 5 heaters. It's also very tough to catch a large fish like that in a net. I used a trout net once to move the fish and it got horribly tangled in it. I had to cut it out(grunting at me the whole time)but still couldn't get all the netting off it's spines. After about a week, it came off by itself. Had to pull it off the filter. Caught it by hand after that, which was still no easy task. If i had a dollar for every time I thought it was going to come flying through the glass!
With all that being said, they are great fish. If I had the space and the means to keep another one, I would do so in a heartbeat. Best of luck!
