Or not? Just watched Darcey Bussell do Tap and it's inspired me to start! But will it harm my ballet training?

I would say it won't really help. The ankles are used completely differently.

It will not harm your ballet training, unless you spend so many hours on tap, that you don't have time for ballet anymore .

TAp and Ballet are totally opposite! I take both but I like ballet more. I take 7 ballet classes a week and 1 tap. I take other types of dance as well. I am taking tap to help me count better.

Kev

Tap will help you with rhythm, and make you a more well rounded dancer...I can't say it will make you better at ballet but it definitively won't hurt either.

Tap will help develop rhythm and musical sense in general, especially if you don't play an instrument because in tap your feet really ARE an instrument. It will also make you more aware of which foot your weight is on at the end of a small musical segment and which is ready to go as the working foot for the next segment. This skill is important in ballet, too, but less evident because you can't hear the difference. In tap it is crucial.

I can't hurt and can help with your timing. I have had some very, talented ballet students, with poor timing and rhythm, and it really helped them with that issue.

Besides, it's fun and it's never bad to know more dance styles. It makes you more "sellable" in the business.