Whats this algae?

[Flynsqwirl]

No! Not my bubble algae that's exploded in proportion, the one on my snail!

 

[samnaz]

ulva or sea lettuce perhaps?

 

[Bret Brinkmann]

Marine Plants in the Aquarium

macroalgae, marine plants, caulerpa, refugium substrate, marine macroalgae for sale

www.marineplantbook.com

Check this site out. I'm thinking Gracilaria hayi. It looks more brown than red though. Mine usually turn clear instead of brownish with higher intensity lighting.