Within this yr alone, I've gone through 5 different canister filters.. Magnum 350, FluVal 404, Rena FilStar XP3, and Eheim 2129 (in that order). In my opinion, the best for any tank would be an Eheim. Their biological setting is far superb and easiest to maintain and clean. Get the Eheim 2229 Pro II, it has a built in wet/dry that can properly reduce nitrate/ammonia levels as well as help balancing your water perimeters.
Many people consider Eheim to be top-of-the-range when it comes to canisters, but there's a pretty hefty price tag attached to it.
Personally, I have only used Eheim filters (so I can't compare), and have no complaints whatsoever: very efficient, and absolutely quiet.
With the ehiems do they leak? is changing the media easy to do?
i saw on big als there is a ehiem made for a 400 gallon tank. the thing costs $239 or something. Is that what you guys are using? I figure if i put a big big canister filter, i can just use that one and no emp 400, etc. also if i decide to upgrade to a bigger tank i dont have to buy a new filter setup.
a 180gallon tank with a filter rated for 400 gallon tank is pretty serious stuff i figure, it should handle anything.
I surely hope Eheims don't leak, or I'd be in big trouble!
Seriously though, those filters are manufactured very well, but regardless of what brand you'll choose, there will always be a few rare exceptions that do leak (like the bad seeds of the production...)
Changing media is pretty easy, since most Eheims have a seperate media basket, which is easy to take out, empty and clean...
The ones rated for a 400 gallon tank are probably some of the best you can get, and I think it would be enough filtration for a 180 gallon tank. The Eheim filter I use isn't nearly as big, but it does a great job in my 80 gallon tank. But you could always add another filter, canister or hanging, to have some extra filtration.
I use two additional internal sponge filters, partly for surface agitation, and partly for some extra (mechanical) filtration...