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The Shadow® Overflow is the evolution of the Synergy Reef® overflow system.


The Only 100% Injection Molded!

Featuring a removable weir for ease of maintenance and our molded design for fail-safe operation. The ultra slim design has revolutionized the aquarium overflow and how aquariums get water into their filtration systems.


Simple to install, plug and play overflow system.


Completely quiet operation when used to our specifications. With years of testing and development this overflow system is worlds apart from anything else available on the market.


Up to 2500 Gallon Per Hour Flow Rates!!!

Front Overflow Box
16″ x 1.6″ x 5.5″ Injection Molded with durable Poly-carbonate material
2 x Removable Weir with VTeeth™ Technology ( Allows you to remove and clean the teeth of the weir)
Bulkheads are molded into the Front Overflow Box. No more separate bulkheads.
Fits aquarium thickness from 1/4″ (6 mm) up to 3/4″ (19 mm)  Glass or Acrylic tanks


Rear Box
16″ x 3.75″ x 7″ Injection Molded Seamless Translucent Black ABS
3 x 1.5″ ABS Slip fittings for easy plumbing
2 x U-Flow™ fittings that allow for compact plumbing
3 Pipe Full Siphon Overflow capability!
Removable Solid Black Polycarbonate Cover that locks into place when closed (reduces noise, eliminates salt creep and light from entering the rear box)

Please see our Q&A Tab for more information.


Key features of the Shadow® Overflow


  • Injection Molded – The obvious main change is that the overflow is now 100% injection molded. This means that every overflow will be exactly the same. Being injection molded also means no glued seams that can leak, it is truly a “One Piece” design. We are the only company that injection molds this style overflow system. Injection molding  and precision 3D CAD designed components allows us more details and features than flat stock built overflows.


  • VTeeth™ – Our new Velocity Teeth allow for an even surface skimming flow into the overflow. This maximizes the surface skimming capabilities of the overflow as the flow rate increases. This also allows us to have a very small water level differential. Injection molded VTeeth™ are smooth without any rough surfaces, this provides a continuous smooth flow.


  • U-Flow™ Pipes – Now included with every Shadow™ overflow is a set of U-Flow™ pipes. We have designed these fittings to maximize space inside of the outside rear overflow box. These compact fittings are not available off the shelf anywhere else. They allow us to fit our 1.5″ Fittings into such a small space.


  • 1.5″ Plumbing – Now standard is 1.5″ plumbing capability. No other compact overflow on the market has the capability to use 1.5″ plumbing on such a small rear box.


  • Locking Rear Cover – Our polycarbonate rear box cover is not just a rectangle piece of material. It is a feature that was specifically designed to have a function. We have designed the rear cover to lock in place when attached. It also features a channel system to keep salt creep and water inside the rear box. With design features to completely stop any warpage of the polycarbonate. No others compare!


  • Universal Fit – This will work on any non tempered glass and acrylic tanks from 1/4″ (6 mm) to 3/4″ (19 mm) Thick! Rimless and Plastic trimmed tanks all work!
  • Polycarbonate Construction – The front box and weirs are constructed out of bulletproof polycarbonate. They are practically indestructible!
  • Locking, Snap Fit Weir – Removable locking weir with our new VTeeth™ for easy maintenance and cleaning. We have designed a simple slide fit that allow for a smooth action when removing the weir in tight spots under the trim on your tank. This means ZERO Clearance is needed to remove the weir when installed under a braced tank! This is a non-magnetic locking weir design that snaps into place.


  • Plumb it to your needs – Rear box allows for various plumbing combinations, including the popular full siphon system. We use our modified version for full siphon. Slip fittings are molded into the overflow rear box. No more bulkheads.


Designing with 3D software allowed features to be added that would otherwise not be possible when building it by hand out of flat acrylic. This overflow system was designed by Synergy Reef Systems in the USA!

Injection molding allowed every part to be exactly the same. Every part is molded with the same tolerance and specification. Unlike hand build models, molding allows the Shadow to be precise in fit and form. With the highest quality US produced Polycarbonate and ABS used in the molding process.


The quality is second to none! There are lots of overflows out there, but this is the best quality available, period!


Includes the following with the kit:

  • Front Overflow Box
  • 2 Removable Polycarbonate Front Weirs
  • 2 Polycarbonate Bulkhead Nuts
  • Seamless Rear Box with 3 x 1.5″ ABS Slip fittings
  • Locking Polycarbonate Rear Lid Cover
  • 2 U-Flow™ 90º Fittings
  • 4 Gaskets
  • Drilling Template
  • Installation Manual


This will be a self install kit. You can drill the tank and install this yourself! Instructions are located here: 16″ Shadow® Overflow Installation Manual

Drilling template is included with the overflow and we recommend you use the template when the overflow arrives to align it perfectly. But if you need the drilling template .pdf it is located here: 16″ Synergy Reef Overflow™ Drilling Template .pdf

16″ Shadow™ Overflow

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