honeeb6,
The most popular choice for a type of filter for a large turtle tank is a "canister filter". These are external to your tank and maintenance is usually easier as a result. It also provides your turtle with the maximum amount of swimming area since it doesn't take up space in the tank. The actual brand and model can be somewhat of a "religious" discussion as everyone seems to have their own favorite.
From many of the posts that I have read, for a 55 gallon tank, the RENA XP3 is an excellent choice for the money (about $100-$150), but Eheim, Fluval, & others also make good quality filters of equal capacity.
When you upgrade to a larger tank later, you could then simply add another similar filter, which would give you the needed effective filtering capacity along with some redundancy. You may want to consider doing the same with heaters (2 smaller rather than one large).
If money is not an issue now and you think that you will definately be upgrading to a larger tank in the foreseeable future, then the Fluval FX5 is probably the best way to go. They have several advantages over less expensive filters but can still be had for a reasonable cost (about $200 online). Again, there are other brands that will do a similar job, the FX5 just seems to have developed a very good reputation in these here parts
Finally, be aware that canister filters (as with other types of filters) require different media (a.k.a. inserts such as foam, carbon, "rings"&"stars", etc) installed inside them to do their job. The media needs to be replaced on a routine basis to ensure proper filtering. So, to be clear, after your initial filter purchase, you will need to purchase new media (inserts) and replace the existing media in the filter on a regular basis.
As Daniel3507 indicated, there is different types of filtration that need to take place. Foam filters typically provide mechanical filtration (for larger particles), while carbon provides mechanical filtration (for smaller particles) along with some capacity for biological filtration as beneficial bacteria form along the surface of the carbon. Ceramic "rings&stars" provide a great deal of surface area while still allowing strong water flow. This provides a great place for beneficial bacteria to grow and provide a significant source of biological filtering.
I personally am a big believer in having more than one filter on an aquarium or turtle tank (i.e. two small/med filters vs. one large) simply because of the importance of biological filteration. With two filters, you can alternate media changes and not significantly (if at all) impact water quality.
Sorry to go on soooo long.....hopefully this is helpful
1 RES, Spike (In new home with 1xPleco, 1xRed Zebra Cichlid, 1xYellow Lab Cichlid)
2 Cats, Blossom & Panda
2 Tropical tanks (plecos, platies, tetras)
2 Handsome Blue Bettas, Blueberry & ?
1 Bright Red Betta, Strawberry
1 Feeder guppy breeding tank
