Join Date: Nov 2012
Location: Wesley Chapel, FL
Yes, try this analogy.
CO2 for plants is kind of like oxygen for you.
Lighting drives plants attempted metabolism/growth rate. Think of that like an activity level for yourself.
So say you are a world class athlete. You are well fed, provide all the nutrients your body needs with good diet. You can run a mile at sea level (lots of oxygen) with no problem. If you run a mile at 5k feet (a little less oxygen), at first you will be winded but your body will adjust and eventually you can do it almost as if you were at sea level. At an altitude at 10k feet (even less oxygen) you will be able to still run the mile but you'll be slower and will take longer to adapt. Say you went to 25 thousand feet where there is a lot less oxygen. If you were trying to travel a mile at that altitude, running probably would not be the best way. You would collapse and not be able to run far at all in between breaks. You could however slowly walk and have less issues and overall travel faster with much less risk to your health.
So if you are CO2 limited, adding more light would be like a person collapsing at 25k feet and trying to counter it by running even faster.
I would suggest going all out at your light/co2 balance for a month and see what happens. I'd start with reducing the light period to say six hours. Leave the co2 on until about 15 min before lights off (using a digital ph meter I can tell co2 drops significantly after 30 min in my tank). I would then either increase the CO2 or reduce your lighting. If you have Ludwigia Repens turning red, you are going to need more than a green drop checker to make it happy. It needs at least a yellowish tint to the green. Mine is more like yellow with a tint of green when the Repens is red and totally healthy.
Anyways, watch the repens and get it growing without curling leaves by adjusting the light or CO2. If you don't want to lower your light and can't get the CO2 higher, find a way to add more O2 and then up the CO2.
While your at it, try to remove as much unhealthy plant mass as possible. You could also use more overall plant mass. That will help. Keep on top of trimming and keep things clean. A dirty tank/filter will have less O2.