Mixed with 20 mm leca and osmocote in a heavily planted (stems, java and floaters) low tech it's been fine for a couple of years. Got some slight blue green cyanobacteria on the east facing window side of the tank over the last summer but it's receded now the days are getting shorter. Never noticed any gas coming from it and it's around 50 mm deep in parts. Keeping a cpd colony, c.pygmy, Otto's and red cherries. Built one of Darrells matten filters with a power head and recent ly added an air driven sponge to mature for another tank. Medium flow throughout the tank. All good upto now. Did notice spectacular growth for the first 3-4 months which has levelled off now.