I have been going through my own algea battle lately, and have been thinking about the whole balance of nutrients a lot. Something that hasn't been mentioned yet, that may sound a little crazy, is to add more coral. You don't have very much coral in there, so If you feed a lot, you will have to rely on all the other aforementioned techniques to keep your params in check. What I think is happening in my tank, is that the nutrients are hanging around too long (not enough coral or other means of export) and the algea is loving it. But, if you run a whole bunch of GFO, the nutrients get stripped too fast and coral looks pale. Obviously we need a balance of many things in our tanks to have the coral thriving. I do notice with a lot of the mature beautiful SPS tanks though, that there is tons of coral. So much so that there is no where for the algea to grow except the glass, or sump etc. kind of like my mother in law's killer flower beds. She has them packed with all these amazing flowers and herbs, and when I asked how she got them looking so good, she said "30 years of weeding!" Which makes sense, flowers and weeds eat the same nutrients, so when you start your flower beds, you don't usually have full coverage by the stuff you want, and weeds grow cause they eat the same thing. And, it takes a while and a lot of work to achieve that balance. Of course that's a loose analogy, but it does have some striking similarities.
So, do I think you should go out and buy 50 SPS coral frags? No, but until you have more demand/coverage by the coral in your tank (stuff you want to look at), you will be fighting algea. Or, you will be looking at pale coral. I made a little contraption for scrubbing and removing algea at the same time (tooth brush with modified bristles rubber banded to the end of a 5/8" flexible tube that I siphon through a filter sock and back into the sump. I mention that because you don't have to do a water change to thin out the algea. It's easy, and if you spend a few mins every couple days, it really knocks down the algea and no water change was done. You have to clean the filter sock, but if you want a maintanance free hobby, I would recommend African chiclids. I have also started carbon dosing at the same time as a means to have the bacteria take the place of the algea. Mind you, my nitrate has always tested zero, and phosphate has always tested very low too. So, I am attempting to swap algea for bacteria. If you started carbon dosing now, you could possibly avoid a lot of the algea, but the reality (as has been stated a bunch of times already) is that algea is gonna happen. iMO it's harder to achieve a balance with a few small corals, they will get outcompeted by the "weeds". So, until your coral grows out or you add more, you will have to do some weeding, with whatever method you like, ATS, GFO, Fuge, giant skimmer, carbon dosing, UV, filter socks, manual removal, or some combination of those items. Good luck!