Need help. Nudibranch pest?

[Perpetual Novice]

I haven’t added any new rock or coral to my tank in months but today I noticed a bright yellow nudibranch about 2cm long moving across the back glass of my aquarium. The back of the tank is rarely cleaned so it wasn’t easy to photograph it through the algae buildup but here are the vest photos I got. Is this nudibranch a danger to my tank? I don’t know what kind it is or how it has been surviving in my tank for so long. I’m worried about my corals or if it’s toxic to the water when it dies.
Can anyone help?

 

[Strawberry]

I haven’t added any new rock or coral to my tank in months but today I noticed a bright yellow nudibranch about 2cm long moving across the back glass of my aquarium. The back of the tank is rarely cleaned so it wasn’t easy to photograph it through the algae buildup but here are the vest photos I got. Is this nudibranch a danger to my tank? I don’t know what kind it is or how it has been surviving in my tank for so long. I’m worried about my corals or if it’s toxic to the water when it dies.
Can anyone help?

I would try to get it out if I were you. They can multiply quickly and they eat zoanthids.

 

[Perpetual Novice]

I would try to get it out if I were you. They can multiply quickly and they eat zoanthids.

but that’s why I’m confused. I one have one small rock with zoas on it. But been in the tank for the better part of a year and seems totally unchanged. It’s a large tank with such a small food source if the nudi eats zoas. And I found the slug on the opposite side of the tank. I took it out but where there’s one there’s probably dozens more.

 

[Dsnakes]

I would guess vayssierea felis. It eats spirorbid and other certain tube worms.

 

[Strawberry]

but that’s why I’m confused. I one have one small rock with zoas on it. But been in the tank for the better part of a year and seems totally unchanged. It’s a large tank with such a small food source if the nudi eats zoas. And I found the slug on the opposite side of the tank. I took it out but where there’s one there’s probably dozens more.

I agree that it looks like a nudibranch and most refers agree that they are a pest. What type of zoas do you have? A lot of times these things can conceal themselves among the polyps and even take on the same color as the zoas that can make them hard to spot.

 

[MERKEY]

Had 3 we bought for aptasia and when the aptasia was gone we found 1 colored like the polyp it was on. We haven't seen any more since I took it out.

The weird thing is these were specifically bought as the ones that only eat aptasia and then this started happening. And it would not be the color of the coral unless it was eating it.

So at the end of the day nature will find a way to survive even if we think they will die

 

[Perpetual Novice]

I agree that it looks like a nudibranch and most refers agree that they are a pest. What type of zoas do you have? A lot of times these things can conceal themselves among the polyps and even take on the same color as the zoas that can make them hard to spot.

About 40 or so heads of cheap eagle eyes. The nudi I found is about 3x the size of one polyp and the color really stands out. I really don’t see any more the more I check.

 

[NanoDJS]

First off nudis come in many many many varieties , and they all have specifically one thing they eat. Alot look very similar to each other , just like the berhgia coerulescens the pic above , and berghia verrucicornis the one that eats aptaisia , now called Aeolidiella stephanieae , they are almost identical. One is larger , and does not get the colors , the blue yellow is natural on those slugs, not from eating zoas like the slugs that eat the zoas . Sea slugs get into alot of crazyness so unless you put it in your tank on purpose , I would say take it out. It looks like the ones that graze in macro , with the long neck and cute little head , but it could be anything .

 

[Lovemyreef2015]

I would guess vayssierea felis. It eats spirorbid and other certain tube worms.

I would guess this^^ or a Caulerpa Slug.

 

[KJ]

I would guess this^^ or a Caulerpa Slug.

Agree Elysia sp.

elysia sp. - - Image Search Results

 

[hllb]

Bumping this old thread. This is exactly what I saw in my tank but didn’t remove. Any update from the OP?

 

[KJ]

Bumping this old thread. This is exactly what I saw in my tank but didn’t remove. Any update from the OP?

Elysia sp. feed on algea.

 

[Reefingpops52]

I would try to get it out if I were you. They can multiply quickly and they eat zoanthids.

Not a zoa eating Nudibranch, I have them and the only time I see them is in the day and the only thing they have been observed eating is algae, ALL algae they even eat cheato so if anything I'd keep them out of your refi if you have one they will also happily eat any nori that goes in your tank. These have a leafy growth on the back with barely visible dark speckles on them Zoa eating nudis have frills on the sides and back that look like bowling pins no matter what zoas they eat they all look the same with color variations depending the color of zoas they are eating.