Skimmer bubble line fluctuating significantly and cyclically, problem??

My skimmers "bubble line" has been fluctuating almost on a cycle of about 10 seconds 80% up the neck of collection cup, then it will drop to about 20% for about another 10 seconds, then within 3-4 seconds will climb back to 80% and hang out there for another 10. Does this mean that the pump has to he cleaned? Im not sure if its blocked since it stays to its cycle, its a coralife super skimmer 65 with venturi air line, hanging on back of my sump