Also might want to think about getting some more plants. Is that anacharis in there? If so you can probably just propogate it as it should grow very quickly in your tank at that light level. Carbon is definately your limiting reagent right now. Your DIY system is either not functioning properly (leak in the line, poor delivery into the water), or your mix is old/bad (or not enough bottles). Are you injecting the CO2
by way of the powerhead I see on the right side?
One other thing I would do is a hydrogen peroxide treatment. This has been highly effective for me battling BBA and staghorn algae, and has also been effective for some battling GW. IMO
it probably would be even better against GW since its a free floating algae that has all of its surface area in the water column.
I'd do a big water change, and right at lights out dose 3-4oz of peroxide into the tank. Make sure you have maximum aeration (ie powerhead on, filter on high). This level should be low enough not to cause any damage to the fish (plants should be fine as well). By the next morning, you should have killed a good bit of the GW. I would probably do the same treatment the next night as well just to be safe. Then do a water change (to get rid of the dead GW as the peroxide is no longer present in the tank). Just make sure you have a NEW bottle of hydrogen peroxide (3% is the commonly sold concentration), and that you cap it tightly when done using.
Here's a thread I picked up on a quick google search:
And the easiest way to get rid of GW (or any particulate present in the water column) IMO
is a diatom filter. In under an hour you can quickly remove the GW which is preferable to killing it, since you don't then have all of the dead algae in the tank to rot. This method obviously does not get rid of the underlying cause which I as well have found to be predominantly from an ammonia spike, made much worse under higher light (I was on vacation and a fish died and rotted for a couple days). But if you have corrected the problems in the tank, it is much faster and better for the plants than a blackout. It's also great for Ich, and if you do a heavy rearrangement of the tank and kick up a lot of crud.
is the easiest of all the algae types to rid from you tank. It does no direct damage to plants, can be killed/removed using a number of mechanical devices (UV
sterilizer, diatom filter), and performs a service when it is present (by utilizing the free ammonia that would otherwise hurt your fish).
I only wish I could have GW instead of the other more vile forms of algae. Goodluck.