1) Only the very top bit of GFO should gently boil. GFO (and carbon) is soft and if it is tumbling it will grind itself down putting GFO (or carbon) powder into the system which is not ideal.
2) The effluent will probably test "zero" on a low sensitivity test kit (like Salifert or API), but you will probably get a low reading on a high sensitivity kit (like D-D Merck).
3) That has more variables than just PO4. That is more of a reading of overall nutrient level. If nutrients are ultra low then you may "never" clean the glass, if nutrients are high the glass may need cleaning every second day. I think you're doing pretty good if you can go 1-2 weeks without cleaning.
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~ Mindy
SPS fanatic.
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