be careful adding any "fertilizer" to an aquaponics system... read the mds, be aware of additives..

not tryin to knock ya uf,,, i understand you're concentrating on the plant aspact of ap, but adding certain things that might be very good for the plants can quickly kill your fish..
a good natural calcium additive is crushed eggshells
are you using an electric toothbrush, or q-tips or anything to shake the plants? or do you have bugs doing the work?