The best place online to learn about octopus is The Cephalopod Page at: <a href="http://is.dal.ca/~ceph/TCP/index.html" target="_blank">http://is.dal.ca/~ceph/TCP/index.html</a>
I have had three octopuses in the last year. The first one escaped through a small hole. The second one was a female. She laid her eggs and died shortly thereafter (that is what they do in the wild). I tried to raise the eggs, but without her there to care for them, it didn't work. The third and final one is a male and is doing great. I have had him for the last two 1/2 months. I have learned a great deal about these fascinating creatures. I have kept them in a 58 gallon tank with and without tankmates. They all would and will eat from my hand. I could go on and on about my experiences. The astoturf or the black plastic that wraps around DLS filters stuffed into small holes will keep them from escaping. It needs to be a very tight fit. They do not like the way it feels and will not try very hard to remove it, but they will try. If it doesn't come out easily they will give up. I have every crack stuffed and the covers weighted down with 24 lbs. of dive wieghts and every cut around tubing for filters is precise. If the proper precations are taken, they can be a great pet. But, heed the the warnings, they can escape through extremely small openings. If their beak can fit through it, they can. That can be an opening as small as 1/4 of an inch! If you are seriously interested in keeping these wonderful creatures, email me at uelkmp@cs.com and I will be happy to help you so that you don't have to go through the same learning curve.