I feed only 2 times a week. No problem (Provide seaweed for the grazers every other day) Heres my take based on my 75G I went through some serious algae issues with.
Cut feeding down..Seriously. Water change 5G *every* week, HOWEVER, you *must* know what the water params of the water you are using to top off and mix with. If there are nitrite and/or po4 issues with your source water, your never going to get ahead. I removed all mechanical filtration from my system...well in the 75 I still use a skimmer, but no 'filters' exist. I have found with out one the water is plenty clear (I also use UV 24 x 7 with weekly 5G wc's) The filter was just a source of ongoing maint and nitrate issues. The tank has been far better without it..Let the LR do its job. Anyway, speaking of UV and skimming, boost them. Slow up the flow through your UV a little and crank up the skimmer. You want to get as much trash out of the system as possible. If your not willing to part with your filters then replace, not clean them monthly. You've got to find the source of your issue though it *sounds* like you are over feeding. This is one of the most common and can take a year or more to start cropping up. Then, boom, "I have an unknown algae issue.." Flake food especially contains po4 and overfeeding builds it up over time until a full blown bloom is on.
Thats my advice.
Peace.