Are you having any particular issue with your tank? Typically, a tank that small would be fine with just water changes and no skimmer.
Look into the hydor slim skim and the slim skim nano. decent quality skimmers for the smaller tanks. You dont want a huge thing taking up alot of space in your tank. Unless you have a sump......then you have more options
180g- Mostly BIG fish and some coral. ~80g Nuvo- My coral tank with "happy fish"~ 90g- FOWLR Not the not happy type of fish~ 125g- Freshwater Malawi Cichlids ~10g- Nuvo- The refugees from the Ich of '18