It's not uncommon, most likely a film of yeast and/or other microorganisms. They need oxygen to survive and grow, hence they are found floating on top of your wine. The wine is most likely fine - it's reassuring that it tastes good - but it's better to address this issue sooner rather than later.
- Did you add Kmeta/KMBS/potassium metabisulfite, if so when and how much? This is often our first line of defense against unwanted microbes. I'd be tempted to add to target 50ppm since you already know there's something growing there.
- How full is your container? Try to minimize the airspace at the top (with the constraint that you don't want it to overflow if there is an increase in ambient tamperature in your basement)
- If possible, i would 'overtop' your vessel before taking out just enough wine to add back your bung/airlock. That is, top up with wine until it just overflows, which will force much of the surface film out. It's a bit messy, but best to get rid of it if you can. It's best if you insert your topping hose beloww the surface, eg siphon from a container of topping wine above your main vessel and put the hose in after priming with wine. I would also spray the top with alcohol or Kmeta once you're done with Kmeta addition and topping.
