I had that, and at first hoped it was the start of feather caulerpa, but it stays small....it was bryopsis...a bad algae. It is on a runner like caulerpa so it shouldn't be hard to remove it at this early stage. It grows fast and is a problem if it gets out of hand.
Never a dumb question...they are very young/small they grow on a single runner (vine) just grab the largest as low as possible and gently pull, the rest should follow right along, if the connecting vine breaks get hold of the next little plant and continue. They grow on the rocks in the beginning, and they don't have good roots.