What is this centipede-like bug? Are they harmful to fish?

grimreefer911 · Mar 1, 2023

Hello, I recently started noticing 2 small white centipede like “bugs” on the glass of my tank. They have antennaes, many “feet” like a centipede, move slowly, and are completely white. The bugs are very small but still bigger than pods. My tank has been fallow for 8 weeks now following a brook outbreak and I am about to introduce a black ice clownfish, but I need to know if these “bugs” are harmful parasites or not. I have a AIO IM 15 gal cube with 10lbs live rock/10 lbs sand. I have not introduced anything new into the aquarium in the past 8 weeks other than a GSP and a reverse Superman monti. The salinity is 1.025, ph = 8.0, temp = 77 F, Ammonia = 0, Nitrite = 0, nitrate = 10, phosphate = 0. Any help is greatly appreciated! Pictures below:

blaxsun · Mar 1, 2023

Looks like a nudibranch.

Tired · Mar 2, 2023

I'd agree it's likely to be a nudibranch. It won't hurt the fish, but may be a coral pest. Check your corals for signs of irritation/pests, and consider dipping them to see if anything falls off. If you do dip them, keep a pipette and/or turkey baster on hand, and a cup of clean tank water, so you can remove anything beneficial or potentially harmless to clean water before the dip kills it.

Cthulukelele · Mar 2, 2023

Do you happen to have any montipora in the tank? It does look a bit like a montipora eating nudibranch. If you do have montis and do the turkey basting test the other person suggested I'd focus on those

grimreefer911 · Sep 3, 2023

Cthulukelele said:
Do you happen to have any montipora in the tank? It does look a bit like a montipora eating nudibranch. If you do have montis and do the turkey basting test the other person suggested I'd focus on those

I did have a reverse Superman montipora that bleached soon after due to the nudibranchs. I think they must have hitchhiked when I first bought the monti. Thank you for all your replies!