Flourish Iron is 10mg/ml Ferrous gluconate. At $9 for a 250ml bottle, that's 2500mg of Ferrous gluconate. Is there a cheaper source for this compound? I'm currently dosing with 2ml Flourish Iron = 20mg Ferrous gluconate a day. If I get 20mg Ferrous gluconate Iron suplement pills (for people) and drop one in to the tank, what will happen? Will the "inert" portion of the tablet hurt the fish?