Hi all I have a 190 litre aquarium with discus and cories plus some schooling rummy nose tetras I do very frequent water changes using half r o water and half tap water my ph is constantly 6.8 with no movement whatsoever the tank has been setup for around 2 years the problem I'm getting is algae growth I have moved the tank as it was in direct sunlight it's growing mainly on my java fern I have a pressurised co2 system but don't know where to look as my next trial as its really beginning to annoy me plus my java moss won't grow it's still green just not growing