I placed a puny looking bunch in my tank and it is really taking off nicely. The "dip and read" type measuring test indicated about 120 ppm GH and I keep the tank at about 4 degrees KH. 3 watts/gallon, PMDD, CO2 injected to 6.8 pH, 2-3 mm gravel enhanced with clay/laterite. It's gonna be a race between the Marsilea and the chain swords.... Tom