Ugh. thenewgreen, one of my three people I actually worked with on a day to day basis at my last job has made turtle soup on numerous occasions. Needless to say, it's one of the many reasons why I did not like him. Turtles and Tortoises are my favorite animals, once I graduate and have some money I'm definitely get a pet turtle. r/turtles is a great subreddit and you learn a lot just from lurking it. It's really cool that you found one today. Hope you became friends with him/her.
I tried to be friendly. I think it got to where it was going. I think I'm subbed to /r/turtles, too. All I can say is, the general recommendation is . . . I think 4x the filtration power you'll need for whatever tank size you have. My recommendation is to double the recommended filtration power. Super cool animals.