Again, my advice is going to be skewed but lets get some background info first before we start into "you should buy this...."
Jay,
Do you use tap water for your tank water or are you using RO/DI water?
What type of algae did you have problems with before? What did you do to get rid of it or is it still there?
What type of filtration do you have on your tank? (If I remember, you have a HOB filter and a skimmer right?)
From there, I think we can come up with a plan. Most people are opposed to adding chemicals to a tank to kill algae. Chemicals do not really solve a problem. You still need to get to WHY your tank has algae. Take one of my tanks for example. I have major blooms going on right now. I have not done a water change in over two month, I do not have a skimmer on it right now, I have not had any clean up crew and I do not pay any attention to it right now. If I test my water, I am sure it will come up 90% clean of any ammonia, NO2, NO3 (Nitrates), or anything else. The algae has already turned it to food. (this is where people have a hard time following this talk( The algae feeds off the NO2 and NO3 in the tank. If you have a major algae field, most if not all of the NO2 and NO3 has already been absorbed by the algae for food. It will not show accurate levels in a water test! Now my problem is pretty easy to fix. Get to the root of the problem. Well right now the problem is an increase of heat in the tank due to my T-5 lights not being vented yet. Another source of the problem is that I have not been keeping up with any maintenance what-so-ever on the tank. And I have not gotten anything in there to eat the algae. So in one or two weekends worth the work I can have this thing in tip top shape. I just need to find the time. Now take my other tank for example. I dare you to find a speck of algae in there. I have not done a water change in two months, but I do have a good skimmer that is keeping up with the waste, I do have a complete ecosystem that takes care of any leftover food and waste, I have set up the system knowing that I want as little of maintenance as I can put into it so when I get busy I do not need to touch it. It did have an algae problem when it first started, a very bad problem, but I got to the source of the problems and corrected them one by one.
So the moral of the story is, a chemical can promise to kill the algae for you but in my 10 years, I have never found one that works and is good for you system. A LFS employee will try to sell you ANYTHING as a cure because they want to make a sale and a quick buck. The one thing you have to remember is, there are no quick fixes in this hobby.