i had a nice reef in my 75g that i got my octo in now. it crashed for a reason my test kits did not know so i kept some fish for a few months, then cashed everything in for my octo, its nice to have the best of all worlds. ive had everything you can think of in freshwater, sting rays, turtles, marine community, reef and now an octo and i would say so far my octo is the most entertaining! but thats just the way i feel....
Not even close to as much sand as it looks . We wanted a beach front in case one we get wants to dig but the depth look is deceptive. We constructed something between a plenum and an undergravel using PVC pipe, plastic peg board, a double lined filter bag and a water pump. The front view shows the sand all the way to the bottom of the tank but is only about 1.5" wide. The beach behind the front gap is only about 1.5" deep and there is only a trace behind that. The rock does not go all the way to the back wall so there is swimming area 360 degrees around the "mountain" overflow and only rock on the back side. The front sand is deeper than I wanted but so far (8 months) there do not appear to be any nasty pockets and I do poke and stirr about once every two months. I had a sand sifting star to help keep it stirred but it had a run in with an over hungry pencil urchin (very little algae for it to eat and I have to supplement with plants - also moved one of the urchins to another tank) and I have not found another locally as yet.
So far so good with the setup (the cleaning - or lack of it - is a major boon) and my first resident, Mercatoris (Carribean pigmy), has survived her hatchlings by 7 weeks. She is getting weak and rarely eats now but still interacts most nights for a few minutes. I expect to try a pair of her hatchlings in the same tank (all five are in a breeder net at the top now) so we will see how it does starting from a young creature next (Trapper started brooding two months after we got her).
Here are pics of the Octopus fortress where we keep Pinnoctopus cordiformis it's some 3000L (950 G). The current inhabitant is feeling anti social at the moment and is hiding up the back of the concrete pipe:
No one is the view from across the room, no 2 is behind the scenes, we can secure the doors if nec and 3 is a view inside the tank. The camera has picked up rather a lot of scratches on the glass sorry (it is 76 years old though )