I completely agree with Purrbox. The brine shrimp won't do anything for you, other than possibly make things worse. And never listen to the people at the LFS, lol. Some of the people that work at fish stores are really uninformed aboout a lot of things, and planted tanks are usually the least known about.
Also, DIY setups that are done correctly are usually much more effective than the systems bought in the stores. Some packages say for up to 40G, but in reallity, are only effective up to about 20G. And if you are wanting something that you have much more control over, then pressurized is the way to go, as you can regulate the output. With DIY, the only way you can regulate it is by bottle size or number of bottles.