You can count on your protein skimmer to remove most of the ink. If it's the thicker, blobby type of ink, you should try to remove as much as possible with a net. We discussed the "panty hose net" a couple of years ago - a regular net lined with panty hose material, very good for ink.
If your octo squirts ink so that it's a smoke screen and the whole tank is black, you won't be able to use the net. I do a small water change - 10 or 20 percent and let the skimmer take out all the rest. Fresh carbon might help, too.
Yes, a 100 percent water change is a lot, especially all at once. However, I can't find from your past posts what filtration you're using or whether you have a skimmer.
Hope all is well in your tank,
Nancy