Sorry but I can't tell anything from your picture. But there are several possibilities. Could be some kind of red turf algae or maybe "cotton candy" algae or some kind of formiferan or maybe even a branching type of coraline algae. Better pics would help as more info about it's texture and ease of removal.
looks like a very calcified bumble bee snail. ive seen a few at work that barely look like bumble bee snails cause their shells have been run over by coralline algae etc.
Strombus maculatus
tiny Strombus snails that reproduce in our tank. They lay eggs on the rock and glass, a small bubble with 3-15 eggs in it. The eggs hatch and the tiny conch chew a hole in it and craw out. The egg bubble is about 1/8 inch or 2 mm in diameter, with white spots in it.
Pictures on the web. These egg bubbles has more eggs than normal seen in my tank.
I do not find them to be great grazer, not like Stomatella snails. They can cause problem with pumps. They have fairly hard shells and can crawl into pumps and jammed it up.
It’s a bit difficult to see in the picture. Is the growth very hard? Vermetid snails can sometimes grow on other snails and that would match the “red branching” part of your description at least.