metals in water

[qxcontinuum]

1) I was just watching a documentary online from Australia. In a marine zone the reef was deteriorating and as a solution against that was sinking an old navy ship.
I though metals are harmfull. However every sunk ship has flurishing coral colonies on them.

2) Can i buy cheap active carbon from home depot and other stores in Canada? It'll be the same?

3) I've read about the magic of Poly Pads in removing almost anything bad including alagae from the tank. But they are very expensive. Are they substituents on the market (maybe intended in industrial or home use)

Thanks again for all further inputs

 

[ccCapt]

1- Iron will not hurt anything in a tank. Of course you son't want to drop a 50lb chunk of scrap metal in your tank, but the phosphate remover GFO (granular ferric oxide) is rust. Also, remember on the reefs there are currents that are constantly taking water away and bringing in "fresh" water.

2- I would not use any cheap, no name carbon. It may leech phosphates and cause more harm than good.

3- Poly pads work great for removing meds from a tank. The only algae they remove is what would get caught up in it. They are expensive and IMO they don't need to be used constantly.