<span style="color: black"><span style="font-family: Verdana">Depends a bit on the water parameters and what media you are using, but I would stick with the manufacturer's recommendations. For example, if your PO4 is really high and you are using Phosban, you will likely exhaust it in a couple of days on the first use. IME, a good GFO lasts quite a bit longer.</span></span>
<span style="color: black"><span style="font-family: Verdana">Try this:</span></span>
<span style="color: black"><span style="font-family: Verdana">1. </span></span><span style="color: black"><span style="font-family: Verdana">Test the water.</span></span>
<span style="color: black"><span style="font-family: Verdana">2. </span></span><span style="color: black"><span style="font-family: Verdana">Use the media dose that is recommended.</span></span>
<span style="color: black"><span style="font-family: Verdana">3. </span></span><span style="color: black"><span style="font-family: Verdana">Test the water the very next day. PO4 should be substantially reduced.</span></span>
<span style="color: black"><span style="font-family: Verdana">4. </span></span><span style="color: black"><span style="font-family: Verdana">Test again the next day. If PO4 is even less, leave the media in place. If PO4 plateaued at an elevated level, replace it and start over at step 2.</span></span>
<span style="color: black"><span style="font-family: Verdana">5. </span></span><span style="color: black"><span style="font-family: Verdana">One of two things should happen:</span></span>
<span style="color: black"><span style="font-family: Verdana">a. </span></span><span style="color: black"><span style="font-family: Verdana">PO4 should get down to acceptable range and not require replacing media very often.</span></span>
<span style="color: black"><span style="font-family: Verdana">b. </span></span><span style="color: black"><span style="font-family: Verdana">PO4 stays elevated, prompting an investigation as to why.</span></span>
<span style="font-family: Calibri"><span style="font-size: 13px"> </span></span>