I put some of my euphyllia and goniopora in a holding tank before moving to my new build. I knew I had red planaria, so I was using FWE. Bought a couple euphyllia and put in the tank also because there were flatworms in the bag. Decided to do a hydrogen peroxide dip on my gonis which have encrusted on an egg crate. 2 of the spider looking critters came off the egg crate. Any ideas what they are?