-about how often to u change various medias
The mech filter may need to be changed once every 5 years. I changed mine once in 8 years.
The bio media you change as needed. Maybe never
-what kind of media does it use
Its fully customizeable. The limit is your imagination. It comes with a sponge for mechanical filtration, bio max pellets for bio filtration (very porous, mote surface area then most media), and a bag of activated catbon for chemical filtration (I don't use it personally)
But you van also use ceramic rings, bio balls, scrubbies, filter floss, poly fill, ect. Skys the limit.
-about how much does each media cost
It comes with everything you need in the box. Additional media prices will vary depending on your LFS. (See options above)
-is it as efficient as a canister filter
Absolutely. In fact, because of the design and the flow rate (much higher then most canisters), it can potentially provide much better mechanical filtration. However some of the high end canisters have advancements that make the biological filtration better.
This is a pretty simple system, but when compared to a basic canister like the eheim classics, they match up. In fact, I think it may havemore media volume. (My AC110 holds all the media from my eheim 2227 canister)
See my diy plumbing thread. Under $5 and a few minutes of your time, can make this great filter EVEN BETTER.
That's all I can think of off hand. If you have any more questions, feel free to send me a PM