Hey! I worked with
O. rubescens for my master's and even tried to rear a couple broods. Let me take the pressure off you: you won't be able to rear them if it is really is
O. rubescens (Ok, i guess anything is possible, but it is insanely unlikely. Unless you are at a marine station or similar facilities, then you may have a fighting chance. I am assuming, however that you are doing this at home). Many very experienced people have tried and failed.
Red spots means that they are developing. However, depending on water temperature, I have had them brooding for over 15 weeks (that was at 11C). Where was this individual captured and what is the water temp you are keeping it at.
Secondly,
O rubescens has planktonic young, (for a picture check out
http://www.wallawalla.edu/academics...s/Mollusca/Cephalopoda/Octopus_rubescens.html) which are much smaller than the other species that people talk about raising on these forums, which is one of the challenges in raising them. As such, they are not likely to take adult mysids or amphipods. Perhaps very young of either of them or artemia, and you may need to add some dissolved organic carbon to the seawater, like perhaps bovine albumin or something.
Ok, additionally,
O. rubescens stays in the plankton for a very long time, to a comparatively very large size, than other planktonic octopus paralarvae (over 3 cm mantle length if I remember right.)
Anyhow, good luck. If you pull it off, you will be the first. Let me know if I can help out any other way.
Oh, and I hope this wasn't too discouraging.