If you are running a scrubber to help remove algae from the display, try first running the scrubber without manually removing algae off of the rocks. This is because when you scrub algae off of the rocks (or if you put a lawnmower or similar in) while the rocks are still in the tank, the algae will float around and die, causing a nutrient spike. It's better to let the scrubber slowly remove the algae for you. This will prevent spikes, and is less work too.
However, if there are LOTS of algae in the display (so much so that the phosphate and nitrate tests are zero), then your scrubber may not easily compete, even after many weeks. So if after four weeks you don't notice a reduction in algae in the display, then slowly start removing algae manually from the display (or, add a small algae eater). Don't remove TOO much algae at once (or don't get TOO big of an algae eater) because that will generate a spike too. Once the algae in the display has been reduced some, your scrubber should be able to take over from there, and all the rest of the nuisance algae should slowly go away.
Note: This does not apply if you remove the rocks from the system before cleaning. Removing rocks can be done at any time, but is much more work.