The CPR Aquatic SR3 Protein Skimmer is an in-sump skimmer that features a newly designed baffle system. Its narrow footprint is perfect for small sump spaces including the Bio-Cube 29 tank by Oceanic. It easily slides inside the middle chamber of the sump section of the BioCube 29 without any modifications (but will NOT work with the BioCube 29 HQI). The lid closes as originally manufactured and the collection cup can be easily removed for cleaning through the rear access hatch.