We often talk about a 10x guideline for planted tanks. This is to minimise dead spots that can result in algae. It's also to ensure that sufficient CO2/nutrients are delivered effectively throughout the water column.
Folk succeed with far less and far more, but 10x is a good rule of thumb. So a 240 litre aquarium has 2400lph claimed flow rate from the filter manufacturers.
It's actually more important to consider how the circulation works throughout the aquarium, and not just rely on numbers. This is where the type of filter outlet is important i.e. spray bars, lily pipes etc. Many folk also add powerheads to their aquariums. I personally find these hugely unsightly and would rather add another filter to get the required flow.
However, if your aquarium is a biotope with no plants then flow rate is not so important. You will just need a filter that is capable of dealing with the fish waste and to provide some circulation for oxygen exchange etc. A 2260 would be fine, especially in combination with appropriate maintenance practices.
