It's always best to go with white vinegar if you can. But, if you really need to disinfect, use a diluted bleach solution (bleach and water) and rinse it a bunch of times. Then rinse it with conditioned water a few times.
Animal testing is a terrible idea; they get all nervous and give the wrong answers.
I just got a used reptile tank too. I'm going to go with vinegar, but that's just because it's a super heavy 55 gallon which would make it really hard for me rinse out well if I had used bleach. I still plan on rinsing, just not nearly as rigorously. Otherwise I would vote for the bleach.