I agree with what everyone above has said. Even if nitrates are low, water changes will replenish the all kinds of trace vitamins and minerals that the fish and inverts need. Water changes will also replenish the ALK
of the water so that the pH doesn't begin to fall.
, I have one friend who has two SW
tanks in his apartment. He hasn't changed the water in either of those tank in about a year. He simply keeps adding FW
to maintain the correct salinity value. I would love to test both the pH and nitrate in those tank. Nitrate would be off the scale and I bet the pH would be in the high 7.0's. I am surprised anything is still alive in the tank.