Identifying what this is

(Sorry if it's bad quality, there's algae on the walls. But that's not the main point I want to discuss.)

There is this brown ball floating in my fish tank. It's not sitting on the decor; it's floating in the middle of the water. I have no idea what it is. The last time I added anything new to the tank was more plants, which was about a month ago. There's nothing else in the tank that looks like this. There's an unidentified floating object in my water.

You nailed it....a UFO

Just remove it if it bothers you, but no idea what it could be from me

Could it be a snail shell whose occupant died and is long gone? Hard to tell as the pic is on the fuzzy side.

Agree. Just remove the UFO if it bothers you.