Hi, Wasn't sure where to put this post but seeing as only the 'c' is missing and its a gas guess here is as good a place as any. What I would like to do is initiate an informative discussion about the importance of oxygen to plants and in particular there health. Now I'm no planted tank expert but if the right levels of co2 are vital then surely so must the o2 levels be of equal significance in the no light cycle. With this in mind I added a large air pump on a timer set to come on when lights are off and the plants seem to have responded well. But I can't be certain that this is the cause as I changed the dosing levels at the same time,(I can hear Clive laughing as I wright ). I always have a constant surface ripple but try not to gas off the co2 to quickly with it, I also have quite a high fish load which is why I'm now looking at o2 or more specifically lack of o2 being a contributory factor of poor plant health and therefore algal outbreaks, not that its a massive issue in my tank. As I said I'm certainly no expert and the above is kind of meant as an opener for an informal discussion on o2 please. Regards, Chris.