My mom told me to ask you that can we use fresh water sand for a salt water aquarium??? We have soaked the sand for three days. Is it better to use powdery sand because the one we have right now is pretty rough.
yes you can use it but only a really thin layer.. maybe about 1cm deep.
Dont use it with an undergravel filter and you will need to have something in the tank like tufa rock or similar to buffer the pH, normal river sand wont do this. To get round that problem i often add a few handfulls of coral gravel, aragonite or similar
Ok now its a little bit difficult, my english is not good enough, but i'll try:
My experiance with freshwatersand ist not that bad, therefore I can follow Colin. The silicate??? (SI) in the freshwatersand let to grow some Algae (Kiselalgen), but if they are to much use an silicat-adsorber.
Fine Sand is better than rough sand in the tank, because the fine sand has a much bigger surface for the bacteria.
The sand should not have sharp edges, that can hurt the skin of the okto.