For a 4 footer, a water turnover of 5000 litres is desirable. I wouldn't rely solely on return pump for water circulation as it is quite impossible to achieve that. Having wavemakers will help solve your problem. When it comes to wavemakers, Tunze is still the best... Seio is a value for money alternative.
But before you rush out and get yourself some powerful Tunze Streams, make sure you sand bed is not too fine... controllable Streams such as 6100 will come handy as you can adjust the intensity accordingly.
On the side note... stirring your sand bed manually may not be a good thing as you will release large amount of toxic into the tank water. Try not to do that... let your starfishes, dollar sands, snails, hermits, sea cukes & etc. do the job instead.