small rock from freshwater tank can use in saltwater tank?

[taowa]

can I use this small rock instead of sand?

 

[heathlindner25]

Not a good ideal,multiple problems.

 

[thegrun]

I don't know what type of rock that is, but generally it is a bad idea. Most will leach heavy metals back into the saltwater, killing corals and even fish.

 

[jayball]

Stick to aragonite based substrate. If you feel the need to have a pebbly substrate than you can use crushed coral but keep in mind that anything that size has a habit of trapping food and detritus and can cause nutrient issues down the line.