02-24-2011, 01:42 PM
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Canister filters are ideal because not only do they do a superb job of filtration, they also are somewhat adaptable with respect to water flow, and that is important. Different types of fish need differing levels of water current. Canisters have a spray bar which can be placed along the end wall with the holes directed against the end glass to allow a quieter flow down the tank--suitable for the forest fish we mainly keep--or remove the spray bar and use the spigot if a stronger flow is required--as for some species of fish that come from flowing rivers.
Eheims are in my view the cadillac of filters. They not only are enormously efficient and effective, they have been around for decades and have the proven reputation of reliability and durability. I have three Eheims, two of which have been running for more than 13 years non-stop with never an issue.
Other similarly-designed canisters are perhaps as efficient--I have one Rena XP3 and this seems to be so--but their longevity is yet to be determined because they are newer on the market. While initially they may be less expensive, if they need repair/replacement sooner the cost savings is gone.
I didn't check the tank rating for the models you mention, but always get the one rated for the tank, not larger; less sometimes works, if one needs very minial filtration/flow. But the newer models now have adjustment for flow which makes this rather pointless, so the one rated for the tank is best.
If the Eheim comes with all the necessary media, fine; mine didn't when I bought them. If they still don't, i would recommend cheaper media. The ceramic disks and biological media made by Fluval which is considerably less expensive, is basically the same thing. Here one can save with no repercussion.