If you are feeding daily, that is basically adding nitrates to your tank. That is what food turns into, even when consumed. If the skimmer isn't skimming well, as most seaclones don't, then the nitrates are left to be removed via weekly water changes. Thankfully, this is easy in small tanks...but even with the 10% weekly changes nitrates can creep up on us. If nitrates were at 20, for example, a 10% water change would only remove 2 and leave our nitrates at 18.
Algae is a complicated battle. There is some reading in my signature about it from our articles section. I'd recommend large water change, see if you can get more skimming out of your skimmer by further adjustment, and changing out your filter media and rinsing out your sponge (you should do this monthly at a minimum).