i use around 1.5 kg for my 2 feet tank in the canister.
they are essentially the same as bioball or ceremic ring in term of function as they house bacteria . however it was claimed that the surface area of biohomes is a lot more than commercial product , thus enable more colonies of aerobic bacteria to house
they are different in such a way that due to their porous surface , anaerobic bacteria can be house in too.
bacteria grow exponentially . like a log curve. they will not fight with live rock
have run the system with more than 1 year . dun think will crash . i put them in a hugh mesh bag and only clean the mesh bag in a while with tank water .
nitrate level just measure 10 mins ago with tropic marine test kit : <1mg/l to 5 mg/l