I know bristles can be good, and most are. With how red these are, (yes most of those pics are the same one), I was concerned of them being fireworms. I saw a couple larger ones hiding in the bigger rock in the back, and I was under the impression only fireworms get big, but I honestly don't know how big those are. I just saw them for the first time a couple nights ago, but obviously they have been in there for a while.
I ask because I am getting ready to set our 65 back up, and move stuff from this 29 biocube to it. Trying to figure out if I need to limit what I move.