Thanks for the replies and pics.
definately gives me some ideas.
I'm leaning toward some type of hinged acrylic / clear screen hybrid.
There is some clear screening I have seen used on reef tanks to help with fish prone to jumping out.
This would help with light penetration as well as heat escpae while also keeping the octo contained and captive.
I have a good reference for custom acrylic work, so I could have him fashion a good lid for a side tank I have plumbed into the main system and easily convert it to hold an octo and stil have a reef enviro.
here's an old pic, but the tank setup is still the same.
The side tank on the right is what I'm thinking to modify with a custom acrylic/screen lid.
I get "This image may only be saved by friends" from that link. Maybe because I use NoScript, but I tried to turn that off and it didn't help. It could be a linux/firefox/flash/amd64 stupidity, though, if it works for other people.
Monty, I get the same message but I do see the picture (just can't right click and copy).
Sharkdude, if you decide on a hinged affair, be sure you do something like 1/3 2/3 or 1/4 3/4 NOT 1/2 1/2. Let the smaller part be the side you will leave down most of the time (in your case, the acrylic side). The smaller tank is hinged this way and all the cutouts at the back worked well with plenty of room to clean the tank in the forward 2/3. We have another tank that uses an acrylic piano hinge but these two are attached with a flat, no pin, hinge and I like these slightly better (the piano hinge may hold up better over time though). The latches on the sides are acrylic hasps from Tapp Plastics and are held on well with only automotive trim tape. If you are going to use this kind of hinged lock, be sure you set the supporting rim so that it is only the thickness of the top OR to the thickness of the top + the thickness of the hasp catch. In the larger tank, we added a rim attached to the tank TOP to support the flush acrylic cover (the same thing can be done with screening). You will need to lock the acrylic firmly on the left and right sides as the acrylic tends to try to bend upward (the thicker the better but it will still have this tendency) heat from the lighting will aggravate the tendency (especially since the water side is cooler). Keeping it latched flat will minimize the effect.