You should be aware that in the normal scheme of things, phosphates cause algae to flourish. As such, phosphates became ‘the enemy’ to marketing weasels who would have you believe that algae are the bane of our existence. Phosphates are not considered overtly harmful to fish in naturally occurring amounts. Phosphate removers will attempt to remove phosphates from the water, but you should know that the products are just an exhaustible resin. Once they have accomplished their goal, and your water is blissfully free of phosphates, you will probably have poor-doing plants because plants tend to require Phosphates, Nitrate and iron to flourish. You will probably have higher than ideal Nitrate levels because they are not being used efficiently by plants. Worse; the fish will soon be fed, and then have a bowel movement, which completely replaces your preciously reduced phosphates. It’s a losing battle. When the phosphate removing resin is completely exhausted, you can replace it and start over again.