I doubt there is a filter inside the tank. Some cars do have the pump in there though!
My suggestion is to fit a filter between the tank and the pump. It will then also protect the pump. It will then be on the low pressure side too. You can position it for easier access to change in the future. Another option is to fit one under the bonnet in the line feeding the injectors.
It is VERY strange that there is no filter in the system. Injection systems need clean fuel to prevent injector problems.
