I am planning an O. habitat for my high school Marine Biology classroom. I have a 75 gallon acrylic tank. A generous Tonmo member has offered the use of a chiller. I am near Monterey CA. I keep my tide pool tank at 56 F. Now I am planning a refugium to connect the chiller to the tank water, provide a place outside the tank for treating the water, and give me a place to keep crabs, shrimp, mussels alive before they go in the tank with O. The refuge I am thinking about would have three sections with water spilling from one to the other. The first and tallest one would have my protein skimmer. The next one would have an undergravel filter covered by coral gravel with a powerhead to pull as much water as possible through the gravel. The shallowest part would be the refuge with sand and a rock in the middle that is above the water for shore crabs (the hate to stay underwater for long). I plan to have easy access to siphon clean the gravel and empty the protein skimmer without having to disturb or provide an escape hatch for the O. What do you think?