The most common pygmies often available are the Caribbean mercatoris. They are nocturnal and would not likely be seen in a 45 gallon tank. I did not find Wiley for 5 months (born in the 45 and escaped the breeder net several times). If you do not have a red night light, it is unlikely you would ever see it. Octopuses in general (including the dwarfs) should be kept in a species only tank, appropriate to their size, with little else in residence (20 gallon for a merc or two). Even with the pygmies, it is an eat or be eaten dynamic.