Hi, Aimee. I don't know anything about easy carbo, but I've had pretty good luck with Flourish Excel. You can get away with doubling the dose, short-term.
A few years ago I had such a terrible BBA infestation that I almost quit the hobby. As an act of desperation, I came up with The Excel Bomb. It worked.
Here's how I did it.
Now, a few caveats about the following method: First, it will only work long-term if your tank is otherwise healthy and balanced. If your water parameters are off, or your light and nutrients are out of balance, or whatever, the BBA will come back. On the other hand, it is my experience that once this stuff takes hold, it simply doesn't die without drastic measures. Second, this is sort of an extreme measure. If your tank is a simple one that you can tear apart, it would be a lot easier to just remove the decorations and boil them or spray the with H2O2. If your tank is too densely planted and/or aquascaped to do that, read on. Finally, I don't get all the credit for this idea, but if you use it I will except royalty payments in the form of pet store gift cards, if you insist.
What you need:
A smallish spray bottle
A bottle of Flourish Excel (Maybe Easy Carbo would work too?)
Enough water for an 80% + water change, temp equalized and conditioned
A way to get said water into your tank in a fairly slow, gradual manner.
What you do:
1. Figure out the dose of Excel needed to treat your tank, according to the instructions on the bottle. For my 55g tank, this was 5 to 6 caps full. Add this dose to your spray bottle.
2. Fill the bottle the rest of the way with tank water.
3. Drain the tank, leaving just enough water to keep the fish reasonably comfortable for couple hours. (2-3" did it for my critters--they didn't like it, but they were OK) You could remove the fish and drain the tank entirely, but in a fully 'scaped tank I find that this isn't practical.
4. Take the aforementioned spray bottle, and spray the living daylights out of everything in your tank. Really get in there and hit things from every possible angle, making sure you get undersides of leaves, shady spots, anywhere this crud might even THINK about growing.
5. Slowly refill your tank with temperature equalized, conditioned water. I use one of these cheap little filters off ebay and a piece of rubber tubing to pump the water back in over a period of an hour or two.
6. It might be a good idea to add an air stone for a week or so, since this will kill ALL the algae thus sprayed, and the decomposing algae can use up a lot of Oxygen.
Over the next several days, the BBA will turn gray or reddish, an indication that it has officially cashed in its chips. Any critters in your tank with the slightest interest in eating algae are going to have a field day.
7. Administer additional treatments as needed, t least a week apart. My tank, which had a very severe infestation, required two such treatments. Other than very small growths here and there, which I can live with, it has not come back.
Good luck. I hope this is helpful to somebody. Thomas