There are a lot of reasons not to use ice cubes directly in your tank. You don't want to have a drastic temperature change in your tank (just as you don't want a big change in sg or pH). Whatever you do must be implemented slowly.
You don't want to have the ice cubes floating there like little icebergs for your octopus to touch (maybe even get his arm stuck on one).
Remove the octopus? You'd have to catch it - not an easy task, and most people don't have another emply tank to put their octo in.
Then too, you'd have to use RO/DI water or you'd be adding water of poor quality to your tank.
There are a lot of better ways to lower the temperature than using ice cubes.
Nancy
You don't want to have the ice cubes floating there like little icebergs for your octopus to touch (maybe even get his arm stuck on one).
Remove the octopus? You'd have to catch it - not an easy task, and most people don't have another emply tank to put their octo in.
Then too, you'd have to use RO/DI water or you'd be adding water of poor quality to your tank.
There are a lot of better ways to lower the temperature than using ice cubes.
Nancy