Yes, you can also do evaporative cooling. They will eat almost anything. Crustaceans (snails, hermits, fiddlers, and the like) are best for them. You can check the octopus availability thread at the top of this forum for online sources, or look around locally. You can usually special order an octopus in. When you do that you are rarely guaranteed the species that is listed, if the supplier decides to take a stab at IDing it at all. You need to have the tank running for 3+ months before you put your octopus in to make sure all the parameters are stable. The setup should run you about $1000 new, if you look around for used make sure no copper based medications were used in the tank because the copper will leach onto the glass, rock, and sand. If you decide to do a chiller, it will probably run you $250-500. The octopus shouldn't cost more than $80.
i know its kind of a dumb question but...........what makes it cost so much,if you could name what i didnt that would be great. . . . a tank filter and lights and stand 180-220$a skimmer about 160$ octopus from 40-80$ and live rock?????????????thats all i know
You can make a setup cheaper than $1000 but it just depends on the equipment you select. New or used, where you get the live rock, etc. If you have a local marine aquarium society you can get all the equipment and live rock you need much cheaper than buying it new at a store. Quality equipment is going to cost a lot of money. A good skimmer can cost $200+ brand new. Live rock can be ridiculously expensive at $7 or more per pound... 1-2 pounds per gallon of water. If you buy a well designed sump that can set you back another $200-$400, or you can build one MUCH cheaper.
Every octopus personality is different. Some will never ink and some will be shy/skiddish and ink often. The best way to deal with it is dim lighting and slow movement around the tank until the octopus adjusts to its surroundings.
A sump is another area for your tanks water to drain to, and then be returned with a pump. It adds to the overall water capacity of the system. In other words, a 30 gallon sump underneath a 75 gallon makes for a 105 gallon system. You can also run a skimmer, heater, or whatever other equipment will fit in the sump, so you don't have to have it all hanging on your tank. Makes it look much nicer, and makes it a lot easier to make a nicely sealed lid. This would also be an ideal place to run a fan to cool the water, since you aren't going to get a very good breeze over a tank with a sealed lid. A lot of people also section off a part of the sump to use as a refugium. A refugium is ideally a "refuge" for things that would be eaten in the display, like copepods (basically tiny saltwater bugs) and in addition keep a sandbed, some liverock, and macroalgae. The point of that is the macroalgae absorbs the nutrients out of the water that would otherwise build up and become toxic to fish, or in this case, an octopus. Of course there is no way to completely stop that, which is the point of water changes, and even still, the macroalgae needs to be pruned occasionally, like weeds in a flower bed. Otherwise it will eventually die and release all those nutrients it has absorbed back into the water.
Here is a really good link for further explanation: