My new sourdough starter is extremely active after just 2 days - can I feed every 12 hours instead of 24?

I have recently started making sourdough, I was given a sourdough starter that was roughly 6 months old, and had been maintaining that, but then the other day I dropped the jar it was in so had to throw it all away :(
I'm making a new starter using a recipe that uses 1:1:1 starter, wholemeal flour and water, and after the first 24 hours it was already very active (even survived the float test). I fed it last night and this morning woke up to it having risen a lot but dropped down to around it's usual size. Is this normal?? Should I feed it just when it needs feeding (so now, after 12 hours) or should I follow the recipe and feed every 24 hours until its a stable starter