[pogodzib]

Yes, they are called hang-on tank (HOT or HOB) skimmers. There are many, many different brands that make them. AquaC Remora and Coralife Superskimmer (needlewheel version) are decent skimmers that are reasonably priced. For the most part, anything cheaper than those skimmers are usually junk. There are several skimmers that are better, but they will cost more as well, so you'll need to determine your budget. When deciding on a skimmer, you'll want to do plenty of research and get one that is rated for double your tank size since most manufacturers rate their skimmers for way larger water volumes than they should be.

BTW - If you have a sump, you'll get much more "bang for the buck" buying an in-sump skimmer than you will with a HOT skimmer.