There are many different answers to your questions as there are people. 10 years ago, we thought anyone with 1 watt per gallon of light was crazy. Today, 1-2 watts is normal and 2-3+ is very common ...

Does she need CO2 at 1.8 wpg? Yes ...

Does she need more light? That is a function of how fast she wants her plant growth to be forced ... personally I really like and prefer tanks in the 1.5-2.5 range, in my opinion, they are easier to maintain - yet still have excellent plant growth rates ...

Now that said ... there are lots of legitimate reasons to make an argument for less light as well as legitimate reasons to argue for higher light ...

There are a few plants that need higher lights ... so if there are specific plants that require high light that she absolutely has to have ... then that would be a legitimate argument for higher light ...

But in general ... she is just fine ...

I have a 180 gallon tank that I normally run at about 2.3 watts per gallon ... but when things get hectic, one of my standard routines is to simply unplug one of the banks of lights and drop it down to about 1.5 watts per gallon ... that quick change reduces a lot of my *problems* <grin> ... for example, I've been finishing up graduate school and for the last year, I've reduced the lighting level down to about 1.5 watts per gallon because I just have not had the time to provide the kind of daily maintenance that I am accustomed to <grin> ... and slowing down the growth rate made it a lot easier to maintain ...

Greg