Two important notes that I was going to touch on are:
How are you testing? What type and brand of kit or meter?
At any rate, the fact that the algae are there means that you have enough nutrients to grow them. Algae are amazing adaptive species but they can't cheat science.
to provide specific suggestions we need specific info. How old is the tank? What's your livestock list? How big is the tank? What and how much do you feed? What sort of equipment is on it (skimmer, carbon, GFO, anything else related to nutrient export)? What is your water change schedule and where do you get your water from?
and (in reference to the peroxide):
Algae is present because of NO3 and PO4. Try to understand the source of them in order to determine the best solution(s).
What is your flow like (equipment used, turnover rate in tank)?
Do you use ro/di? If so, any TDS?
What do you feed, how much, how often?
Do you ever do any large water changes in addition to the auto changer?
What's your substrate like? Do you frequently sift it and your live rock with a power head or turkey baster?
Here are a couple of water change calculators. The first gives a view of how much original water is left based upon your change amount and schedule. The second pouts more emphasis on how dirty the water is to begin with and how much pollution takes place each day. I don't think that you'll know that if your algae is keeping your readings so low.
I geek out on this kind of crap, so I was interested in comparing our percentage of water changed. It looks like I change 30%/month, and you change 40%/month. So, it sounds like either your changes are taking less pollution out of the system, or I've got other things going on in mine that remove nutrients (fuge, activated carbon, carbon dosing, etc).
http://www.hamzasreef.com/Contents/Calculators/EffectiveWaterChange.php
http://www.theaquatools.com/water-changes-calculator