There are exceptions to LFS employees. Some are very helpful. The person that gave the poster info wasn't very knowledgable.
Wow 30g tanks for $30...thats a good deal! Hopefully you can get them!
So you have 100 watts over that 10g? That is a
huge invitation for algae! I'd only use one bulb and then get some type of CO2 setup along with some plants. You can make a DIY setup...just google DIY CO2. Light will not be a problem, but the size plants grow will. I'd get alot of fast growers though, just to outcompete algae. Some good plants are Bacopa caroliniana, Moneywort, Ludwigia, Echinodorous tennellus (foreground plant), crypts, anubias, Hygro (will grow really fast). Head over to the Aquatic plant forum for more help. There are probably some folks on here that have high light 10g tanks (or close to that). Plant choice is a bit harder when the tank is smaller.
I really suggest you only use one 50w bulb. You will have a tank full of algae soon...especially with only one plant. Even 5wpg is high light...10wpg is an overkill!
Could you post a picture of that plant so we can ID it? I've never heard of a "goldfish" plant, so I'm interested in knowing what it is.