you need more air from what you say,what you didnt say is how big your res was. I think there is a post on how many watt pump for how many gals. is required. fish store pumps are ok but lack a little on air out put. the advantage is they are quiet,I have used in the past a 4 outlet fish pump with 4 - 6 inch stones in 1- 5 gal. bucket,just an example the more bubbles the better