I don't know what kind it is, but that looks like a biofilm.
Biofilms form in liquid when some microorganisms manage to float on top of a liquid and reproduce and/or more microorganisms attach to them. It may or may not be one kind of microorganism.
If you've had this three times, and assuming you cleaned the crap out of everything really well, you may want to consider replacing any scratched or plastic gear (hoses, buckets, carboys, cups, spoons). Not that plastic is bad. Many of us use plastic with great success. It's just that plastic is more likely to harbor unwanted bugs than glass. If you get it again, replace the glassware too. After three times now, you're probably to the point where losing beer is costing more than replacing some gear.