Every once in a while, the aquarium just looks like garbage. The water is kind of dingy, the corals all look deflated, and the fish are not too impressed with what is going on. The quickest solution to this problem is a good water change. Water changes are like enemas for the aquarium, purging out all of the bad stuff and giving the livestock some relief. If you follow it up with a fresh batch of carbon and a good skimmer cleaning, then your tank should look good as new. Of course, this is just a generalization as some tank problems don’t just go away after a water change.