Black spot on glass

[h4wk]

Hi guys, I'm pretty new to this hobby and currently in the process of cycling my first ever aquarium. It's a 200 liters one and it's been about a month now. Today I woke up and saw this black spot on the glass. It's a bit less than a centimeter and it's alive. Probably something that came with the live rock. My question is, is it harmless? I would assume not but I figured this is the perfect time for my first post here [emoji5]

 

[TheEngineer]

Possibly a stomatella snail. Could be a slug. Does it have a small shell on its back?

 

[vegamedic]

hard to tell without a better picture. try to focus on the spot/critter or remove it from the tank and take pictures of it in a (gloved) hand

 

[h4wk]

Ok, I turned the pumps off to take a couple of good pictures, looks like a sea slug to me and it this case it should be safe right?

 

[Skynyrd Fish]

Human eating nudibranch?

 

[taxiem]

I would have said nudibranch personally xx

 

[TheEngineer]

Can you see a small white shell on its back? Might be an elephant slug.

 

[h4wk]

Can you see a small white shell on its back? Might be an elephant slug.

It seems to be black all around and hasn't moved a lot all day. I wonder if it enjoy the massage from the pump that points to where it has stopped [emoji4]

 

[h4wk]

Aaaaand here is one more picture of my first (as far as I know) alive and moving inhabitant of my tank. So excited [emoji3] I'm right to assume it is harmless for the tank then?

 

[Jose Mayo]

Nudibranchs usually have very specific diets ... if you do not have your specific food growing in the tank, will die.

Regards


Edit: By its appearance, it is a Dendrodoris krebsii nudibrach, it feeds on sponges.

 

[TheEngineer]

Oh yeah, definitely a nudi. Didn’t see the fancy butt.