Camshaft Ramrod;3756936; said:Even if you know of the tank size, I still feel it not good to buy an appropriate fish. It might just be me, but I would never buy someone a fish without them first OKing the exact fish. There's alot to consider. I always tell people NEVER to buy me a fish. This is just my take on things.
If anything, get him a betta and be done with it.
When I finally got a decent sized tank about 15 years ago it was a 125 and I had basic fish such as Oscars and a florida Gar and a few others. My girlfriend at the time decided to surprise me with a new fish and put it in the tank when I was not home. It was about a 7" Buttekofferi and it beat the snot out of just about everything in the tank and killed both Oscars in about 4 hours so I'm definitely against buying fish for anyone without them knowing. But seeing as he doesn't have any fish I would recommend talking to someone at a lfs about what size tank it is and what fish will not outtgrow it and can live in it forever and also what fish you can put together in it peacefully. Good Luck.
