Depends on what`s in the tank. I would think maybe 4-5 days. Some ways phosphates can get in the tank is your old filters and RO
membrane. Could also come from your food. If it was me I would cut back on feeding to every other day or even every three days. I would run your lights only 3-4 hours a day. Remember it did not start over nite and it wont go away over nite. One more thing I would do is frequent PWC
`s and when you draw the water out try to siphon as much algea out as you can.