Use a chopstick, lots of detritus really needs to be powered out of crevices and I don't think gentle currents will really stir it up.
As for the water changes, its not just the trace elements that need to be replenished. With zeovit, I do believe they actually want you to reduce your water change frequency/volume. Because you're adding all of the bacterial population, food for them and then whatever else (sorry I can't remember exactly what else you're supplementing with), you'd be disrupting those populations and their food source every time you did a water change.
I just can't see zeovit really benefitting you in this case and it would probably be a waste of money as you wouldn't see the results you were looking for.
Just my two cents
