I don't want to speak for all the species of GSP out there, but I think most if not all of them have the same care requirements. Good filtration always helps everything, so you're on target there. Lighting and flow would be the two limiting factors off the top of my head. The brighter and more intense the lighting, the better growth you will see. Logically (for instance), if you have a 96w PC over a 50 gallon tank, chances are you're not going to see the growth you would see when they're under HO T-5's or halides. GSP also absolutely love flow, so go ahead and try giving them a little more flow and see what happens in a couple weeks.