@Michelle Yuen hello Michelle! The post on IG was specifically for the Psychedelic batwing slug! There are more sea slug species of course, but In general you usually don’t have to worry too much about it, compared to other animals like shrimps and octopuses where a red light make all the difference! :) Using a red light will give you more opportunities to get more shots! But it’s not as crucial for just nudibranchs in my opinion :)