I appricate your frugalness on the bulbs but I am telling you that your going to only increase your algae problems by continueing to run a PC
bulb that is older than 9 months. As the bulbs age their specitrum output shifts from mostly blue output to mostly red spectirum output. now that does not mean the light looks red. It will most than likly look more yellow than blue but it wont look red. The algae in your tank will favor the red light specitrum that the older bulbs produce. In addition to the specitrum shift the lux output of the bulbs will drop with age. Our eyes are not as sensitive to this drop over time because its not a sudden drop its a gradual one that we really never pickup on until we change the bulb and light up the new bulb and you will be amazed at the output difference. The corals you have may be doing ok under the curret bulb with its age but as the bulb continues to age your corals will find they are not getting enough light and will suffer aswell.
If your serous about getting rid of this algae you must know if there is a phosphate issue in your tank and the only way of knowing this is to test for it. Now your lfs
may do phosphate tests for you but its not very convient since you really need to test your tap water for phosphates, your clean RO
water right as it exists the filter, your clean ro
water thats sit in what ever storage vessle your using, your ro
water after you have put some of the food you feed in it for a period of time.
This will help you narrow down where the phosphates if they exist are comming from. While its possible your ro
water is clean of phosphates if your food introduces phosphates than any left over food in the tank will add phosphates to the water and they will build over time.