Len, Yes running GFO but not Phosban. Reason is with a regular test kit PO4 is zero, with a HANNA HI 93713 Photometer - Low Range Phosphate tester it is .02, that is why I didn't run the Phosban. Guess it is worth a try and see, you might have a point! I already have Chaetos in the sump on a...