Originally Posted by pomps
Um, that seems a bit of a contradiction - either it's a Fresh Water
tank, or it is a Salt Water Fish Only with Live Rock
The Eheim is a very good filter, and it's really difficult to "overfilter" a tank. The amount of flow may be hampering if you have a big canister on 20g or so, but a 75g is pretty large, so it can handle almost any canister filter out there just fine.
The Eheims are widely regarded as the "best" canister, but they are also the most expensive. The Rena XP3 (which I have on my 75g planted tank) is almost as good, and much cheaper. In the end, it's preference.
Also, if you are buying this filter new, then I would go with the Eheim 2128 Pro 2 that comes with a built in heater, since that eliminates a piece of equipment from the tank. HTH