Ok, I have a tank with a large piece of driftwood in it. My snail population seems to be struggling. For snails like my ramshorns that are always visible, I don't think I have a single adult ramshorn whose shell isn't entirely white and pitted. I've tried putting coral into my filter and tank but that doesn't seem to help much. Is there any additive I can use or special food I can put in that will give them a calcium boost? Can I simply buy calcium tablets at the drug store and plop one in?