i use the paper towel thing on my tank at school because it doesnt even have a skimmer. just take paper towels and lie (in a single layer) them flat on the top surface of the water very carefully, then slowly pick them up and throw them away. do this about 5 to 10 times. i have to do this about once a month or every two weeks on the tank at school. just be sure you have a trash bag right by the tank so you can chunk the sopping paper towels in as soon as you pick them up out of the tank.