I have AC 500's that have been running non stop for approx 15 yrs without issue, on 100+ gallon tanks. No need to add a canister to good quality HOB filters such as AC's. That, and they can still be purchased when on sale for under $50!
IMO for the most part bio-filtration media is highly overated. Most of you probably have enough bio-filtration media to handle double the pay load that your current media has to offer. I know that I certainly do.
A LFS south of me has a 325 gallon 'show tank' that at any given time contains approx 80-100 adult cichlids. I don't believe that I have ever seen a fish under 6", with most of them in the 7-9" range, and some in the 10-12" range. In other words there is a huge bio load in this tank. All of the fish in this tank always look very healthy, and the water is always very clear.
The filtration ......... three AC 500's. (now called 110's)
No bio-max rings, lava rock, bio balls, pot scrubbers etc, ...... just sponges, and floss.
The maintenance routine is approx 40% water change weekly, with the filters only getting cleaned when they get gunked up. (as in the water flow slows down) That display tank has been running that way for approx 20 yrs.
IMO unless your tank is stocked with wall to wall fish, I think many people would be surprised at how much media volume is required to keep a tanks bio filtration running in prime condition. Many years back when going to view a tank for sale the owner showed me his 90 gallon koi tank. (72x16x18) which held 12 koi, the smallest being 10", the largest 17". (I put a tape measure up against the big boy) Although the tank water was anything but crystal clear, none of the fish showed any signs of stress, or illness, and they had been in this tank for the entire winter. The filters didn't appear as though they had been cleaned for some time.
The filtration - two AC 500's, one positioned at each end of the tank, facing each other, and nothing more than sponges as filter media.
The bio load in that tank would have exceeded any 'normal' tank that I have ever seen, or I suspect will ever see again.
Not that I would recommend doing this on a heavily stocked tank, but I've cleaned all of the filter media in ALL filters on my tanks, on the same day, and never had any sign of ammonia or nitrites. (not the ceramic rings) The bio-max rings, along with my tank decor, etc, hold enough bacteria to easily handle the bio load in my tank.
With 40 Bio Max rings at the top of each filter chamber (7.2 square meters of surface area per ring), the Bio Max rings alone have approx 288 square meters of surface area for bio filtration, in each filter, and that's not even counting the sponge, or the finer blue/white filter pads that I use in my AC filters. And of course, there's much less costly media one can use than Bio-Max rings. I scored mine at a local auction 15 yrs ago for next to nothing and have yet to replace any of them. I simply rinse the bag of rings when required, and if they're getting plugged up, it sure doesn't show.
Unless you have VERY limited space for bio media, or have small ponies swimming in your tanks, I suspect that any of the filters (and media) mentioned in this thread wil provide ample surface area for proper bio filtration.
But most of them probably won't hold up for 15 years or better.
