You said: "The filtration efficiency of life rock is much lower than that of other mechanical devices. It cannot support as many fish as others. "
then if I use 'shan wu bone', (i.e. no life creatures except fish and my crabs) wil lthe filtration efficiency be better?
A better way to provide adequate filtration is the installation of a protein skimmer. It can remove soluble organic matters before they turn into nitrate. "Shan Wu bone", you mean coral sand? They can provide large surface area for the attachment of N-bacteria. They should have better filtration power than that of the life rocks.