I have a tank just a little larger than that with a Rena XP3 as the only filter on it. Having said that, I know there are people who think the XP3 is too small for my tank and insist that higher flow rates are a must in a tank. Various theories are held by people about how big a filter needs to be. The people who do heavy plantings will tell you that you need to turn over the water volume 10 times per hour to minimize the chance of getting algae in the tank. My Rena come nowhere near that kind of flow rate. Others will tell you various numbers around 5 times the tank's volume per hour. I use a simple rule that seems to work for me. I never get a filter that is only rated for my tank size. If a filter says it is good for a 50 to 100 litre tank and the next one in the product line said it was good for 90 to 150 litres, I would choose the larger of the two for any tank over about 70 litres. I find the manufacturers are a bit too optimistic about how big a tank their filter can serve while I also disagree with the extreme flow rate crowd. One of the main things to look for in a filter is easy of cleaning and ease of priming. All of the filters will do an adequate filtering job on a tank the size they are designed to serve but some take much more effort to maintain than my Rena filters do. They are self priming after cleaning and have a good shutoff system for the hoses so that you don't need to do anything fancy to remove the filter to a place where it can be cleaned. Internally, they have all of their media contained in simple baskets with no need for internal gasketing like I experience in my Marineland C series. The C series are also very nice filters that look much like a Tetra-tech would in the UK. They require manual priming when they are cleaned and have complex baskets with internal gaskets to direct the flow in them properly. In essence, the inlet flow goes through the baskets in a formed piece that amounts to a short section of pipe in each basket. Because the flow path is pieced together, the gaskets are needed to reduce bypass flows. I have no experience with the Fluval and Eheim externals so I have nothing good or bad to say about them. Both filter lines have many fans here on the forum.
