Can co2 scrubber be attached to anything else besides skimmer? How else can it be plumbed? I currently have one scrubber connected to reef octopus but want to add one more scrubber and not sure how I could hook it up.
Just connect two scrubbers together serially. One runs into the next, and it uses up the first one completely so when you change media you move the partly used canister to the replace the used one. Nothing else in the tank or sump has the same air water interface as your skimmer. That's why a co2 scrubber works.
Yes you can use an air pump and air stone. But – it’s always a but – you will not get the same good result as with a skimmer. The reason is – as Gablami indicate – the air/water interface will be much smaller, both in volume and in time.
If you chose to use this equipment – it´s a good idea to get an air pump there you can put a tube on the suction side and connect the scrubber to this tube.
If you have a sump or somewhere there you can use an internal skimmer – you can use one internal skimmer without a skimmer cup in addition to your normal skimmer – it works very well in order to aerate the tank - with fresh CO2 free air.