Depending on the opening size, an octopus can put its arm into the slits along the device and lose part of an arm to the impeller. You may be able to place a net over the device to prevent problems. It would decrease circulation (I do this with my Koralias) but but should keep curious arms out of dangerous dark places.
This is the netting I like best (the vendor is not special but this one shows the three typical sizes available). I recommend something zippered if you can make one work as it is far easier to clean. If something zippered is not available, then velcro would still be much better than a draw string.
I have not seen this kind of water circulating device. If you end up using it, please mention how well it moves the water.
The maxspect Gyre flows a lot. Much more then a normal flow pump. There has been a lot of issues with these as a snail or piece of anything get caught up in it and pretty much destroys it. The idea of this pump is great but I would not rush out to buy one until they get a little less delicate. They run about 200-300$