The Reef Octopus Classic 90 HOB Protein Skimmer is built for aquarists who don't have a sump but still want real protein skimming instead of hang-on filtration alone. It mounts directly on the back of the tank, pulling water through a cylindrical reaction chamber where a needle-wheel pump shears it into a dense field of micro-bubbles. Dissolved organics stick to those bubbles and rise into the collection cup as thick, dark skimmate — pulled out of the water column before it ever has a chance to break down into nitrate and phosphate. Best for: reef, FOWLR, and mixed saltwater tanks up to roughly 90 gallons Setup: hang-on-back, no sump required Pump: needle-wheel design tuned for fine, stable bubble production Maintenance: collection cup lifts out for easy weekly cleaning Because it runs external to the tank, the Classic 90 HOB is a straightforward retrofit for all-in-one and standard rimmed aquariums that were never plumbed for a sump. It's the same Classic Series build quality — cast acrylic body, self-priming pump — just packaged for hang-on use.Compatible replacement parts: Reef Octopus needle-wheel pump parts and collection cups sized for the Classic 90/100 HOB series.
