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Marine Depot Overflow Box OF-800


Item #: MD8139

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High quality and economical hang-on overflow box allows you to easily add a sump, refugium or wet/dry filter to your system. U-tube design allows for easy and convenient installation. Adjustable pre-filter hight allows you to adjust the water level inside your aquarium.

  • 1" Bulkhead
  • U-tube
  • Noise-Reducing Cylinder Foam Sleeve
  • Nylon screw and wing nut
  • Surface Skimmer Box
Model Tank SizeMax. Rim Size Overflow Body
Surface Skimmer
Max. Flow Rate Drain Size
Nano up to 30 Gal1.5" 4"x2.5"x8" 4"x1.5"x6" 200GPH 3/4"
OF-300 up to 60 Gal1.5" 6"x3"x10" 6"x2.5"x6" 300GPH 1"
OF-800 up to 120 Gal1.5" 8"x3"x10" 8"x2.5"x6" 800GPH 1"
OF-1000 up to 150 Gal1.5" 9"x3"x10" 9"x2.5"x6" 900GPH 2 x 1"
OF-1200 up to 200 Gal1.5" 10"x3"x10" 10"x2.5"x6" 1000GPH 2 x 1"
OF-1800 up to 320 Gal1.5" 12"x4"x10" 12"x2.5"x6" 1600GPH 1-1/2"

Manufacturer information

Marine Depot was started in 1998 by a self-professed reef geek and pre-med student Ken Wong. Ken envisioned a one-stop shop where customers could find everything they needed, from technical product specifications, reef aquarium information, expert advice on the hobby and friendly one-on-one customer support. Having grown from a one-man crew to being one of the world’s largest suppliers of reef and marine aquarium products, this very core philosophy still lives strong in the Marine Depot culture 20 years later.

4 Stars


Reviewed on
July 10, 2020

Yes, I would recommend this.

Best for the dollar

Pros: Very durable and simple

Cons: Lack of directions

To be so much more lower priced this product, pound for pound onthe dollar, is the best investment I have made! Thanks Marine Depot for your great design and to be cost efficient!

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Reviewed on
March 13, 2020

Yes, I would recommend this.

Great overflow for those without a reef ready tank

Pros: Value, low noisy, great flow, easy setuo

Cons: Short siphon Prime tube

I did a lot of research before I went with the marine Depot. I almost went through with another brand, boy I'm Happy I didn't. I have since replaced my hob, with a new sump, skimmer and tumbler. Within 48 hours my tank began changing for the better. This thing is quite, works great after stopping power and restarting flow. Easy enough to prime. I did have to use my own air line as the one provided is not long enough to get to the back of the tank for me. I matched it with a 950gph water pump and having no problems. Does not make a gargling sound but does provide enough air to my sump that I get a great deal of bubbling in the wet portion of my sump. The provided cover is great.

Was this review helpful? 2 0


Reviewed on
December 14, 2019

Yes, I would recommend this.

Great Product

Pros: Reasonably quiet, robust, inexpensive

Cons: Lack of instructions

It gets the job down. The black internal box fits nicely into the tank and if you have a black background, you can barely see it. It's reasonably quiet, not completely silent, but the added lid is a nice addition to reduce the noise. Comes with a small vinyl tubing to get the air out and start the siphon, but the lack of instructions might bring trouble to those who have never had HOB overflow before. The bulkhead is a slip x slip. Came with a small scratch, but it came in nicely packaged and it's incredibly well-built.

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Reviewed on
March 25, 2019

Yes, I would recommend this.

No directions

Pros: Cheap and effective

Cons: No directions

It is put together well, u get a spare utube, the noise isn't too bad if u use the provided sponge and keep the lid closed. My only issue was the lack of directions. Not even the video on the website showed how to begin a siphon. Had to watch 6-7 utube videos till I found one that showed how to do it

Was this review helpful? 1 0


Reviewed on
March 18, 2019

No, I would not recommend this.

Broken piece

Second time I had them to send a part that was broken and it still came to me broken so I had to glue it myself or ill be waiting forever to get a none broken part.

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Reviewed on
March 15, 2019

No, I would not recommend this.

Wrong parts

It came with broken and wrong parts and its been over a week and still waiting on the parts to show up!

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Reviewed on
January 15, 2019

Yes, I would recommend this.

Great Product and Features.

Pros: Quiet, has a cover on the overflow, well constructed.

Cons: This might be operator error, but it took me a while to figure out that I needed a slip fitting to connect to the drain pipe. The threads on the outside of the drain pipe are for the ring to secure it to the overflow box.

The box has a clear cover that helps reduce noise and evaporation.

I wanted to add a sump to an existing aquarium, so this was the obvious solution. If I was starting from scratch, I would probably go with a built in drain.

The stand-off pipe had a little clear piece of tubing attached that is supposed to help with airflow to prevent gurgling and flushing sounds. It eventually broke off while I was cleaning the overflow. I could have glued it back on, but the overflow box was quieter without it.

The internal box has a lot of slots in it, which I think helps keep the water currents low so that fish don't get sucked in as often. My previous box had less slots/less overflow area, so I would regularly have to pull fish out.

The siphon tube does get dirty with algae so I take it out to clean every so often. The OF-800 has enough space that I can install a temporary second tube so that I don't have to shut off the water pump while the main tube is taken out for cleaning. It does help to have very flexible airline tubing to start the siphon. It also helps if your tank water doesn't taste too bad. :O

Lastly, the water level in the tank stays at the same level, but level in the internal box sometimes goes up and down. When I see changes in the water level of my sump, I first check the internal overflow box since it might be holding some additional water. If I reposition the siphon tube, the water level goes to the normal level. I don't have any concerns that the tank will overflow; I just have to check the real levels before I decide to add more water.

Was this review helpful? 5 0


Reviewed on
December 31, 2018

Yes, I would recommend this.

Marine Depot Overflow Box OF-800

Pros: Awesome

Cons: None

I bought this for my 125 gallon tank. I had bought a smaller one for my 40-gallon breeder which worked great.

Was this review helpful? 3 0


Reviewed on
October 25, 2018

Yes, I would recommend this.

Very Well Constructed

Pros: sturdy

Cons: none

This overflow box is very well built. I can't wait to get the rest of the parts I need to get this installed on my tank

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Reviewed on
September 03, 2017

Yes, I would recommend this.

Good Value

Pros: Easy to setup.

Cons: Handle carefully as parts can break, Can be loud and adjustment may be needed

I purchased this for my 55gal tank so I could replace my canister filter. So far, I'm pretty happy. The air tube was broken when I received the item but Marine Depot offered to replace it promptly. A small dab of aquarium glue did the trick however and no new parts were needed. You do have to adjust it a little before it's silent. True to the description, the siphoning starts automatically if there's a power outage or break in the cycle.

Was this review helpful? 4 0

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