Hi Reedsburg...
I totally agree with previous posts in that you need more LR in your system. It acts as a great natural filtering system. Add it slowly at this point though to avoid any possible die off which could cause a spike...how far away from you is the closest LFS where you can obtain said LR?
I have to disagree with the previous poster about your system not be a young one at only 6 months along. It typically takes a much longer time for the tank to establish and become stable. This could potentially take years to go through different kinds of algae problems and other things. There's a huge learning curve to this, but it's a very fun and rewarding experience. You'll love it once everything stabilizes and you can see the progress that you've made.
Also, in a 75gal more flow wouldn't hurt either, that would definitely help with the algae problem. Be sure not to overfeed (I sometimes let my fish go every other day feeding rather than every day... especially during the summer months when lighting is a bit more drawn out from the longer days.
Where's Reedsburg? LOL...
Lisa