16" Shadow Overflow - Synergy Reef Systems

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  • How to install the Shadow Overflow - BRStv How-To

16" Shadow Overflow - Synergy Reef Systems

79% Recommend this to a friend (11 of 14)

SKU: 210377

reg. $199.99

Special Price: $159.99

In Stock: 159
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Quick Overview

Up to 1500 GPH Flow Rate

Synergy Reef Systems Shadow Overflow is one of the most sought after overflows on the market today. Here at BRS almost any tank we set up will incorporate the Synergy Reef Overflows for their extensive feature list and reliability.

  • Low Profile

  • Injection Molded

  • Removeable weir

  • Failsafe operation

  • Completely silent

  • Years of research & testing

Note: 65mm drill bit required for installation (sold separately)


Full Details

Install Guide


Drilling Guide


Low Profile

The low profile design of the Shadow Overflow makes it perfect for reef tanks, along with other types since it does not take up that much space inside of the tank. The internal portion of the overflow is only 1.6" thick at its widest point allowing you to fully aquascape your tank without worrying about corals growing into the overflow box.


Injection Molded - Made in the USA

Allowing for tight tolerances and 1-piece construction Synergy Reef removed many points of failure that other overflows have. With no glued seams and strict quality control every overflow is now identical. Synergy Reef is the only company using injection molding techniques for this type of overflow design.



The tapered design of the VTeeth™ keeps the water level in the tank much more steady with flow changes and fluctuations. The increased surface area of the VTeeth™ increases its surface skimming ability directing the dirty water down into your sump to be filtered.


Removable Weir

Keeping your weir clean will lead to much more effective surface skimming and filtration ability. The snap-fit weir will securely mount to the Shadow Overflow and can easily be removed for maintenance and cleaning. Also, the design of the VTeeth™ makes cleaning them much easier than standard overflow teeth.


Failsafe Operation

Having different plumbing methods available with the Shadow Overflow system, the most common and suggested overflow method is the Bean Animal system that uses 3 dedicated drain pipes. The three pipes include; the main drain, secondary drain and an emergency drain making the overflow system completely silent and failsafe.


Years of Research & Testing

With years of real world testing and design, Synergy Reef has designed and tested numerous styles of overflows allowing them to incorporate all of the valuable aspects and designs of different overflow systems into the Shadow Overflow. There are a couple of clones out on the market, but none are built and tested and built like the Shadow Overflow system.



Min tank thickness - 1/4" glass or acrylic

Max tank thickness - 3/4" glass or acrylic

Front Box

  • 16" L x 1.6" W x 5.5" H
  • VTeeth - easy to clean weir design
  • Molded Bulkheads


Rear Box

  • 16" L x 3.75" W x 7" H
  • 3x 1.5" ABS Slip Bulkheads
  • 2x U-flow fittings
  • Removable Rear Cover


What's Included?

1x Front Overflow Box

2x Removable Polycarbonate Front Weirs

2x Polycarbonate Bulkhead Nuts

1x Seamless Rear Box

3x 1.5" ABS Slip Fittings

2x U-Flow 90º fittings

4x Gaskets

1x Drilling Template

1x Installation Manual


Items 1 to 12 of 14 total

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  • Unfortunate By Richard on 8/1/2017

    I used the word unfortunate because the design of the box works wonderfully and is very quiet once you tinker with it.

    Unfortunately the molded plastic is very brittle. I cracked in three pieces and ended up creating a puzzle of patches I fabricated with a sheet of acrylic and a heat gun and plastered on with weld on. I was very careful when I installed pipes and sanded each one to make it slide in easier because fit was extremely tight. They still split the seams. I also don't believe the measurements for your interior pipes are the best for quiet operation. I had to dr mine and create something that worked because the fit is so tight I am afraid to remove the pipes from the box for fear of cracking it again.

    Honestly if I had not drilled my tank for this specific overflow I would have sent it back.

    I have however after all the issues had no other issues in its operation and it functions quite well.
  • Just Buy It By Scott on 7/11/2017

    I ended up buying the Synergy 16 inch overflow as I wanted their Synergy sump with 3 1.5 inch drains for plug and play. You never wished you had smaller drains. I drilled the tank with the fish in the tank after lowering the water level. The nicest overflow made with no noise and the safety of 3 drains. Well made and should last a long time. Would recommend highly!
  • Great overflow By WWIII on 7/7/2017

    Beautiful, slim design and quiet overflow! It can handle a lot of flow and remain silent when installing bean animal style. Wish it came with a drill bit. Also use medium cement, do not use abs to pvc transition cement. The first one I purchased I used abs transition cement per thw old instructions and the reaction cracked the overflow. I've since purchased and installed 2 more using medium pvc cement and they work wonderfully. Synergy Reef stands by their product and sent me a replacement overnight when the first one cracked due to the wrong glue.
  • Very nice By Tony on 6/23/2017

    Installation was easy.. I paired this up with their sump and plumbed it with 1.5" overflow.

    The wier is a little hard to pop out but other than that works like a charm. Well worth the money.
  • Almost Perfect By RB on 6/12/2017

    First, I'm not sure you can buy a better overflow, so I give this one high praise. It seems like every overflow has an issue or is just shy of perfect, but this one is pretty close and it's demons are the least of any. As of now, it's running great and no complaints, but I can see where there would be issues.

    The pro's first. It looks fantastic, the low profile in the aquarium is great. It's near silent at the correct speed. The installation was easy. My first time drilling glass and installing an overflow like this and it went perfect.

    Not really a con's list, but more of a tips list.
    - The plastic is fragile imho, I wish it was stronger. They say install all of your piping and then install the overflow last, but I'm not sure that's always doable all the time. Even with doing this, tightening the union valves, I thought I was going to crack the drains. Just be careful!
    - The drains are an inch and a half wide. Why? It's unnecessary, you can't achieve a flow that would require this. Even if you did, I don't think you would want only one of these on your tank if your tank required 1.5 plumbing. They should have kept the drains at 1 inch. Maybe I'm missing something. Also, good luck finding three 1.5 inch union valves that you can place next to each other. You will have to stagger them. I used 1" reducers.
    - The U shaped drains they give you are multiple pieces pushed together. Mine broke down the middle at the joint. It probably doesn't matter, but still.
    - The original instructions they gave said "use abs to pvc transition cement", then they changed the instructions to say "DO NOT use abs to pvc transition cement" Gave me a heart attack. I asked them about it and they said it doesn't matter, just that a lot of people dont use the transition cement correctly. If you use regular cement, do not use purple cleaner.
    - Do not use sealant around the gaskets (in case you thought about it)
    - The gaskets have two different sides but it doesn't matter which side goes which way
    - The weir is not easy to take off, it's a total pain. I wish they used magnets on a high end product like this. They do give you an extra weir which is nice if you decide to take one off for cleaning.
    - The water drops far in the inside box. They could have changed this with a quieter fall level. In order to quiet this down you have to have the water level on the outside box really high. This is dangerous in my opinion. Why risk it being like half an inch to an inch from the surface. The issue is that the outside box drops down alot. Totally unnecessary, they could have had it come up more. It would have solved the issue. I have a 75 gal DT, so my return pump doesn't push hard enough to make the sound a problem but I could see an issue for people with bigger tanks and higher flow rates.
    - They make it almost black so you can see inside, right? But it's too "almost black". You can't see inside it at all. I wish they just made it solid black to 100% stop algae growth or made it more see through to see if there is an issue. It's at a strange "not useful" transparency
    - Small complaint, wish the template was bigger so that you could align it to the top of the aquarium and know 100% for sure that it's perfectly aligned. It's not an issue to align it if you measure 5 times, but feels like a small thing they would do to make your life easier.

  • Well made but needs some adjustments. By Cody on 6/5/2017

    The box looks really good inside the tank. Very sleek. I have just a couple of issue with the product. For one if I have my power heads on at all the surface agitation makes a lot of noise in the inner box. This is because there's a large drop between the inside box and the outside one. Even after raising the water level to nearly the top of the outer box it's still loud. My second complaint is how difficult it is to get the weir on and off. It should be magnetic, so you can just snap it on and off.
  • Outstanding product at a great price By Eddie on 5/25/2017

    Way ahead of any box out there for looks and safety. With its all black construction, inside and out, you do not even notice it. Very quiet for all the water volume. Would highly recommend!
  • Garbage overflow By Brian on 5/16/2017

    They claim that the "injection molding" to form a one piece overflow is superior, but it isn't one piece. There are seams down on each drain...and the one I bought is cracked. Of course you can't tell this before you install the thing, so I had everything all plumbed in, waited 2 days for the glue to dry and when I turned on the pumps, leaked like a sieve from two of the 3 drains. I couldn't figure out where the leak was coming from at first and just assumed it was from an improper joint I glued. Slathered glue all over the joint, waited for it to dry and still leaked. Upon further inspection I determined that the leak was coming off the overflow itself, and not much I could do at that point. Maybe get some flexall to fix it...but paying $160 for this I would just assume I wouldn't have to go through all these hoops to fix their flawed design! I'd stay away from this product at all costs. Never again will I even think of buying ANYTHING from Synergy!
  • GREAT By Ashish on 3/19/2017

    I send this overflow directly to my tank manufacture so they could make the 2 holes for ideal water line. So glad I found this as I was looking to purchase a simple box and silicone it to the back panel with 1 drain. The price seems high at first but when you factor in that you get all the internal plumbing parts its really perhaps $30 more but with the added benefits of having multiple drains and silent operation.. good buy
  • Disappointed By Scott on 3/19/2017

    I'll start off with the negatives... It is NOT completely silent without mods\deviating from the included instructions. There are several sources of noise. The outer box is too low compared to the inner box and is the source of some of the noise as the water falls into the inner box. I contacted the manufacturer and their suggestion was to raise the water level in the outer box to 1/2" below the top of the outer box. That is ridiculous. While this does make the inner box silent since the water does not have to fall very far it is uncomfortably close to overflowing onto the floor, causes accelerated salt creep from the lid, leave very little room for the emergency overflow pipe. In the end I have the water level I the outer box adjusted to be about 1 1/2" from the top of the box, I added a course foam to the inner box to stop the sound of falling water and I had to add a little very course foam inside the outer box in front of the pipes connecting the two boxes.

    The 3 1 1/2" drain pipes are way over sized for the volume of water the inner box can handle. I have all three reduced to 1 1/4", with the main drain pipe reduced even further at my sump down to 1". This 1" pipe further has a valve on it to reduce the flow because the inner box can't flow enough to keep it full of water and running silent with a trickle of water flowing to the second drain. WithoIt the valve the hole in the top of the u pipe whistles loudly. All of this is with or without the foam in place. The top of the second drain and u pipe are about 1/2" from the top of the outer box lid and the emergency pipe at about the same level.

    The indicated water level on the template had no water volume associated with it. I assumed it would be close to the boxes advertised flow rate.. It seems that to achieve the 1500 gal/hr flow rate you must have the take water level at the very top of the slots. I wish the template would list several water level and approximate flow rate for each. This would have better help me choose the proper drilling position. Now I'm stuck with the box higher than I would have liked. I used a dremel tool to extend the slot further down to help a little with this and to lower the distance the water has to fall to help with the noise.

    The plastic template was a nice touch but I would have preferred a solid one that wouldn't crush when clamped instead of the corrugated one they provided.

    The outer box lid fits nice and tight. The 1 1/2" pvc pipe only fits inside the u pipes and inside of the outer box about a 1/4" but I would have preferred a little more

    The inner box feels solid and looks good in the tank. But the outer box has some flex to it and bows out when full of water and the lid is not on. I would have preferred the outer box was more transparent to help with diagnostic\adjustments.
  • Best Bang for the Buck By JCA on 1/23/2017

    I think this is the best overflow you can buy right now. Perfect for my 120g.
  • Amazing! By HyphyMike on 12/22/2016

    I purchased this for my 20L and it performs fantastic. I cant hear it at all. Ever.
    Its built amazing!


Ask a question

Product Questions

Can I use schedule 80 bulkheaf or does it come with the necessary bulkheads?
Question by: Garnett Miller on May 25, 2017 11:22:00 PM
Hi Garnett, The shadow overflow comes with all the bulkheads required to plumb through your tank. It also includes the bulkheads to connect standard 1.5” PVC plumbing.
Answer by: Charlie (Admin) on May 26, 2017 2:58:00 PM
The note in the Quick Overview states that a 65mm drill bit is required but the installation guide says that a 63mm or 2.5" bit is required. Will either work??

Question by: Steve on Dec 16, 2016 8:37:00 AM
Hey there,
The difference between a 63mm and 65mm bit would be minimal and either would work. As we don't carry a 63mm bit option, we recommend our 65mm as an alternative to the manufacturer's suggestion, which will also work.
Answer by: Zack (Admin) on Dec 22, 2016 4:18:00 PM
Does this take a 65mm hole saw, as stated on here, or a 63mm, as recommended on the Synergy page?
Question by: BC on Dec 18, 2016 10:45:00 AM
Hey there,
The difference between a 63mm and 65mm bit would be minimal and either would work. As we don't carry a 63mm bit option, we recommend our 65mm as an alternative to the manufacturer's suggestion, which will also work.
Answer by: Randy (Admin) on Dec 22, 2016 6:32:00 PM
Will this Shadow Work of a 300 Gallon 3/4" Acrylic Or should I get the 20" Shadow?
Question by: Robert Walter on May 24, 2017 9:59:00 PM
That may depend on the thickness of your acrylic, but you may have issues with the maximum flow capacity limitation as the 16" can only handle 1500gph of throughput at most. I would most likely suggest moving up to a larger overflow or multiple overflows depending on your desired tank turnover.

Happy reefing!
Answer by: Zack (Admin) on Jun 1, 2017 5:17:00 PM