Hello there! I had the same problem a few months ago. Test your nitrates, high nitrates stimulate algae growth and are not good for your aquarium. Algae consumes the detritus in your tank, so having some algae is actually beneficial! I know algae is unsightly and can take over your tank, so I continued my weekly water changes (and sucked the algae off the rocks but left some in the sand bed) I pushed some of the algae around and covered a little with sand. I also introduced a great little clean up crew to help rid the detritus in my tank! My friend (who got me into the hobby and studies marine biology) brought over some beneficial bacteria too! It's been a few weeks and my algae has diminished substantially! I also recommend a circulation pump if the algae is growing in one particular spot--it could be a dead spot! Make sure that you're not overfeeding because this tends to cause a buildup of nutrients and higher nitrates. Hope this helps Best of luck!!