What is this please!

[offshore80]

This has been lurking around my reef at night. I don't see it when the lights are on. But catch it early in the morning with a flashlight. Anyone see this before. I haven't added anything to my tank in over a year. It's the black spot in the middle of the picture with the white line in the center. It seems to have antena
Thanks[

 

[offshore80]

Another picture.

 

[promisetbg]

I have one of those..I got it from my boss.He calls it a sea hare..though I suspect it is really some type of skirted or fleshy limpet.I like it..it eats algae and causes no problems

 

[offshore80]

Thanks!

 

[bang guy]

Elephant Slug aka Black Skirted Limpet.

 

[offshore80]

Thanks, you nailed it.