08-09-2011, 11:47 AM
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I have Eheim canisters on my 90g and 70g tanks, and they've been running now for about 15 years without a problem. Eheim are very well made, and are not only superb filters but have the track record to justify their higher cost. I honestly don't think you can do better than Eheim. I also have a Rena XP3 on my 115g, and I like the filter; it has not been around long enough to compare durability with Eheim, so while it is less expensive, over time it may not be if it needs replacing or repair.
For the two smaller tanks you mention, a canister or sponge on the 3-feet and a sponge on the 2-foot would be my preference. On the 3-foot you could go with an internal "sponge" type, I have an Eheim internal sponge, it is just a single sponge with a small motor and the unit hangs in one corner; they don't make these anymore, but another member recently mentioned that Fluval (I think it was Fluval) make something very similar. I like this unit because you have everything together and it takes up no more space than a dual sponge that would have to be connected to an air pump. Air pumps are certainly more noise than the other, so if that is an issue where your tank is placed, something to consider.