Sounds like a blue green algae. If a image search confirms, you can do a blackout or dose with anitibiotics. I find that BGA appears when I leave the lights on for a couple of days. It can also indicate a lack on nitrate. -Paul -----Original Message----- From: gsas-member-bounces@thekrib.com [mailto:gsas-member-bounces@thekrib.com] On Behalf Of Jeff Sent: Wednesday, December 02, 2009 4:22 PM To: 'Greater Seattle Aquarium Society member chat' Subject: [GSAS-Member] Does activated carbon in a filter leach phosphate into your water? Is this bad for the plants? My amazon swords have some of their leaves covered in a dark colored slime; could this be caused by too high of a phosphate level? I don't have a phosphate test kit yet to check the level; Thanks, Jeff. _______________________________________________ GSAS-Member mailing list GSAS-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/gsas-member _______________________________________________ GSAS-Member mailing list GSAS-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/gsas-member