You put your contaminated fish into native waters...and that's wrong. Communicable diseases are not gonna argue...fish like that ruin ecosystems when they transmit diseases from the tropics.
Going a little overboard aren't you? He didn't take a tropical fish and put it in an alien environment, he put a fish back into the lake he caught it from, and from what I can tell, it never even went into a tank, and was held in a bucket that contained water from the very lake he caught it in.
Still it is probably not the best idea, but to suggest he is going to ruin an ecosystem is beyond hyperbole. People buy live shiners all the time at bait stores, and no one ever screams at them when they use them in a lake or pond, how is this any worse?
