Im pretty sure that they look like what they eat. I have had at least 4 or 5 in my tank. I think i have pics of them all.
The first one eats orange encrusting sponges.
I also had one that ate my gorgonians. Plucked both of them out.
I had lettuce sponges like in the second picture that i caught in Florida.
Never figured out what they ate but it probably looked leafy.
I also had some that looked just like the garden slugs but they were a 1cm long and green and white. Thought i had more pictures of them but the other ones were so camoflaged that you wouldnt be able to have seen them anyways.
I have done plenty of research on the berghia nudibrach and all they eat is aiptasia and mojano anemones. Without them they starve to death.
Just clearing up the misunderstanding. The realy beautiful ones probably eat polyps and sponges or are even extreamly toxic. But the diets range greatly between one speicies and another.