herring/sardines are a good source of Ca, Mg. If they're in olive oil the oleic is good too. Not to mention all the nutrition thats in the guts of the little fishies.
Plus good protein. Vit. A, D. And also dimethylaminoethanol. Calcium pills are like p 0 r n, an attempt at a substitute for the real. Sort of like paper money too.
People love fake stuff it seems, like a bass will hit on a Rapala or Daredevil, or a trout on a fly. Didn't someone once make a comparison between money and a fishhook somewhere along the line ?