I just change the direction of flow.
Just have the flow hit the back wall, add more holes to the spray bar, shoot most of the current into the wood/plant beds etc to reduce the flow. This can keep those dead areas under the wood good and clean. You can also direct some of the flow downward intio the gravel layer.

Play around with it, you should be fine with that filter on that tank size.

Regards,
Tom Barr