I don't know if I believe all this to be true. This whole algae topic has me really frustrated lately, and I'm not even having problems myself. I'm just struggling to understand all these theories. The whole "out compete" thing has my head spinning... I mean, we dose ferts in to the water column, we have lights on all day, nutrients are always present, so how is it a competition if all is readily available for plants OR algae to utilize during our photoperiods? And the abundance of nutrients claim is a crock to me as well, more often different types of algae are contributed to a LACK of nutrients, or bottoming out on one... I've seen multiple claims of 0 nitrates cause BBA, 0 phosphates can cause GSA, and so on... You should be able to grow what ever plants you want in a high tech setup, just because they are deemed low light, doesn't mean they're not going to grow faster in high light... They definitely will. I've had Anubis nana in a med-high light setup sprout new leaves ever few days, and that is a low light plant.
Really, I think what I'm trying to say is, you have to find the right balance... If 6 hours is causing you problems, back off an hour and see how it goes... I know it sucks, but a short photoperiod is better than staring at a tank full of BBA for 8 hours. Research what different types of algae are typically caused by, and try to fix the problem. And even if you do fix the cause, it takes A LOT of effort on our part in the way of cleaning, water changes, trimming affected leaves, etc., to make sure the algae doesn't have a chance to come back. The more you get out, the cleaner your filter, etc., the less chance you have of fighting it again. Make sure your params are spot on(nitrate between 10-20 and phosphate between .5 an 5) and adjust your photoperiod and co2 to what works. Wow, I really just went on a good rant there... Good luck!