I'd say your list is complete, except you forgot the live rock! That's the "LR
" part of FOWLR
. (Fish Only With Live Rock). FOWLR
tanks often don't have protein skimmers because fish will tolerate higher nitrate levels more than corals will. That's why you'll see different "maximum" levels of nitrates listed for Reef tanks versus FOWLR
In my opinion, I'd still shoot for low nitrates even with a FOWLR
tank. Excessive nitrates may not be detrimental to the fish, but they do give nuisance algae food to eat. The more pristine you keep your water, the less headaches you'll encounter with algae and cyanobacteria.
Cannister filters don't substitue for a protein skimmer - they do different things. In a tank without live rock, the cannister filter will serve as a biological filter. With live rock, a cannister filter will serve somewhat as a sump and also for a place to run chemical media like carbon, etc.
You're correct about the filtration aspect of the plug-n-play units. Most folks throw away the bioballs and replace it with live rock rubble. I still like the mechanical filtration though... as long as you methodically clean/replace it at least weekly.