An rw4 would work well. At times it could be too strong. I use one on a Nuvo 20 gallon. I'm also using a tunze power supply and run it at a lower voltage just to get the perfect flow with out creating a sand storm
Just decided to buy a new rw-4/pp-4 it is the new name came in a pp-4 box. I am amazed how small this. I replaced the hydor 425 gph by this and what a difference chose
W1 and the lowest speed. Can not believe how strong it is could not keep any higher. If anyone has better setting willing to try.
If you would like to try the other settings you could get a variable voltage power supply and run it a lower voltage.
Something like thishttp://m.fish-street.com/12v_to_24v_power_supply_for_jebao_rw__fs__wp-60_wp-40_wp-25_wp10_replacement_pump