Thanks for all the advice. I think i have the underlying causes sorted out. I've added a temporary HOB filter for more water flow and I'll darken the tank for a few days. I'll let you kniw how it turns out later in the week. Hopefully i won't loose too many shrimp to the new filter. Jesse Doerr Field Service Engineer FEI Company (503) 267-9620 jesse.doerr@fei.com _______________________________________________ GSAS-Member mailing list GSAS-Member@thekrib.com http://lists.thekrib.com/mailman/listinfo/gsas-member