It's probably thread or hair algae.
Florida Flag fish will gobble this stuff up.
http://faq.thekrib.com/algae.html#hair
Florida Flag fish will gobble this stuff up.
http://faq.thekrib.com/algae.html#hair
Wow, I missed that one!150 watts on a 7 gallon tank? Holy cow you're really in deep with that one.