Protein skimmers are the workhorses of our aquarium filtration, but they also can be quite sensitive to water conditions. Unlike most filters, which simply trap free floating detritus in foam pads, protein skimmers are terrific at accumulating dissolved organic waste and depositing them into a collection cup, completely removing them from the water column. Unfortunately, however, the performance of these bubble blowers can be a bit touchy. Fluctuating water levels or an overload of organic material can send a skimmer into overdrive. Increased oils in the water (from certain fish foods for example), can essentially kill any kind of bubble production temporarily. And when topping off the aquarium with freshwater, the skimmer can lose its mind. When making any changes to the tank (feeding, topping off, etc), be sure to monitor the protein skimmer or just shut it off for a short time. This way you don’t end up overflowing the collection cup and dumping tons of old skimmate back into the aquarium.