have a 4gal. what size hanging filter/ powerhead should i get

[iretthepirate]

i need more flow, bought this tank off craigs list not sure what the rating is on the hanging filter is but i deff need more waterflow!! theres practically no flow on the bottom of tank. mainly lps coral in it. input appreciated

 

[spacetime]

Mod an AQ70 for a fuge, but use an AQ20 impeller if its too much. I also have Steve T's insert and have mixed feelings because it lets flow through the side.