Somehow I ended up introducing cladophora into my tank. EI dosing, 2x39W T5HO 4'' about water level on a 30 gallon, pressurized CO2, drop checker green-yellow, water circulation is good, I stay on top of trimming so it remains good. It hasn't gone wild, but there's a few strands here and there that have attached themselves to a few leaves and in some fissidens. I've used H2O2 to spot treat (with filter turned off, spot treating with a syringe, letting sit for 15 minutes before turning the filter back on). That has seemed to help, but has not eradicated it. Unless anyone has some better suggestions, I plan to continue to remove what I can by hand and spot treat with H2O2. Excel is out of the question for this tank as it will kill the fissidens. I know this because it's happened to me before. So... any other suggestions?