Octos usually leave echinoderms (starfish and the like as well as urchins) alone (there was one recent finding of starfish in the stomach of an octo but I can't remember the species). There have been a few anecdotal incidents that suggest Bahama stars and possibly large green serpents may trap small octos and kill them (it is not known if the animal died first but the stars were found eating a denned octo). We typically recommend staying away from sharp pointy things (like rock urchins) more because octos don't go around things, they crawl over them and scrapes and holes can lead to infections that are very difficult to treat. I have no experience with the Chaeto in an octo tank. I have put it in with a net with baby cuttles but I don't like the stuff in a display because it breaks apart and makes a mess after awhile, others love it.
After super, I will see what direct info I can find you on the red lighting. I think we have an article or two but I have used it for so long I fail to remember the location of the initial write-ups on light color sensitivity. Not sure why anyone would recommend blue as it is not particularly good for most nocturnals for the same reason. I suspect it is more a human observation preference rather than a comfort for animals. If you have a reference for the post on red, I would like to read the source (on topic links are always permitted).
Sorry if I over explain but the experience levels of our members range from people with PhD's in the field (we are hoping to have a panel discussion at TONMOCON VI broadly topiced something like, "What do you do after your ceph degree?") to people who have never had an aquarium so how much is too much is sometimes hard to guess, it is never meant to be insulting.
After super, I will see what direct info I can find you on the red lighting. I think we have an article or two but I have used it for so long I fail to remember the location of the initial write-ups on light color sensitivity. Not sure why anyone would recommend blue as it is not particularly good for most nocturnals for the same reason. I suspect it is more a human observation preference rather than a comfort for animals. If you have a reference for the post on red, I would like to read the source (on topic links are always permitted).
Sorry if I over explain but the experience levels of our members range from people with PhD's in the field (we are hoping to have a panel discussion at TONMOCON VI broadly topiced something like, "What do you do after your ceph degree?") to people who have never had an aquarium so how much is too much is sometimes hard to guess, it is never meant to be insulting.