18 Gal Tank... Doing Filtration Wrong?

[luv*my*fishies]

I have an 18 gallon tank with about 15 lbs of liverock in it. I also have a filter that hangs over the side of the tank, from waht i have been reading.... this is probably not the best thing to have. My only questions are... what is a skimmer? and do i need one??? and should i take the filter off of the side of my tank? let me know! (more liverock?)

 

[SkiFletch]

No skimming is necessary on a tank that small. I'd take the regular man-made media out of the filter, buy a small piece of LR, break it up with a hammer, and put the rubble in there. That way you keep the flowrate of the filter (good) and remove the man-made media's ability to trap detritus and cause excess nitrates (bad).