I'm not Sammy but what I do is use my syphon hose to syphon out a couple of gallons (dragging the syphon along the tank walls and sand bed) then add it to the main tank. With no real bio-load on the "pod tank" and all the caulerpa the water params are great. Then I put in fresh aged saltwater. Like doing a water change, only the water goes into the main tank. Once a month. HTH