hmmmm I don't know much about salt water aquariums, but I gather you are trying to have a tank with out any filtration??
Don't get me wrong poris type rock is excellent for gathering "good" bacteria, but you would still have to have pump to move water across or thru the rock to get biological filtration.
Back in the 80's the "Natural" aquarium was all the rage. This was a tank with no filtration, but utlilized plants to provide oxygen and they supposedly thrived on the bio load to keep your tank clean. It is possible to make this work, but you must have many many plants and very small fish. Guppies and livebearers were the fish of choice.
In a Lake Malawi community, the fish would get too large and either eat or dig up the plants. The size of the fish would produce more bioload then the plants could consume, so I don't think that would work either.