Okay, so I am getting ready to do some research on intraspecies learning Octopus cyanea (Hawaiian Day Octopus). I have chosen this species because I live in Hawaii and will be able to catch wild octopuses to be my test subjects. I have recently aquired a 125 gallon aquarium that I will set up as an octopus tank, this aquarium will be linked to another 75 gallon aquarium. I am a little worried about filtration though. I am on a college budget and cant buy expensive equipment. I am going to make my own sump, refugium, and protein skimmer and will run several kinds of bio-filtration. I will also have a copper filter that all of the water runs through. I am hoping that this will be enough to be able to keep the octopus alive and well. I am going to feed the octopus live crabs and other crustaceans that I will catch in the wild. I have a few general questions. First, I just want advice on whether or not this set up will be adequate to maintain chemicals suitable for octopuses. Next, I was wondering what people think of UV-filters because I am thinking of getting one. Finally any other general advice on how to keep an octopus and not spend a fortune or on behavioral research in general would really be appreciated. Thank you very much.