Part 09 Saltwater Tanks DemystifiedPlumbing: Sumps, & Refugiums

Table of Contents

I) Introduction

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II) Refugiums

A refugium is literally a place of refuge, and in the saltwater aquarium hobby, it can be a refuge for algae, fish, corals, inverts, really anything. But that being said, most hobbyists use a refuge for a couple reasons:

When used to grow macroalgae, a refugium is a great phosphate and nitrate reducer.  As the algae grows, it will consume phosphates and nitrates, and then to remove it from your system all you have to do is remove a portion of the macroalgae and voila, nutrient export is accomplished!

There are a couple ways to set up a refugium: HOB or in-sump.

1) HOB refugium

AquaMaxx HOB-R

A hang on the back refugium is a great option for those systems that don’t have sumps, but still want to benefit from everything a refugium has to offer. A HOB refugium is basically a specially designed power filter, that gently circulates water and that has a clear back panel so you can attach a light and grow macroalgae.

Just like a larger in-sump refugium, depending on the size, you can add a substrate, pieces of rubble rock, miracle mud, ceramic media, and macroalgae. The cool thing about a HOB refugium is it is a short distance to travel between the fuge and tank, and that means more pods will survive the journey and provide food and filtration to your display tank.

If you have ever considered getting a Mandarin Dragonet, a refugium filled with amphipods and copepods is an absolute must.

1) In Sump Refugium

Marine Depot 30" Elite Sump by Trigger Systems

If you have a tank with a sump or are considering upgrading to a sump, then why not consider a refugium.  An in-sump refugium is my preferred method of adding a refugium, primarily because it is hidden away and doesn’t detract from the beauty of your display tank.

Typically, a refugium section of a sump is either directly after the protein skimmer section, or at the very end like in the MD Elite Sump pictured below.

The larger size of an in-sump refugium allows you to just have more of everything: more amphipods and copepods, more macroalgae, more nutrient export, and more biological filtration

In either the HOB refugium setup or the in-sump setup, you will need to add some sort of light in order for the macroalgae to grow.  I really like this grow light by Finnex.

Finnex Refugium Plus LED

III) Plumbing

Alright, so this section is not a “How-To” section.  That would take way to long and is extremely complex.  Rather, we want to give you an overview of the different ways saltwater aquariums are plumbed.  Not only will this help you understand the topic better, but it will also help you choose your next system based on your needs and goals for the hobby.

Let’s get started with overflows.

1) Overflows

MD Elite Overflow Box

An overflow can be internal or external, but regardless of the type, the function is the same.  An overflow transports water from your display tank, down to your sump, and then back up again. For a beginner, you pretty much never have to worry about this, because the tank you buy will have already made the decision for you.  But knowing about overflows is both helpful if you want to build your own tank, or if you are going for a certain look or filtration style.

Your standard internal overflow works well, but takes up a large portion inside your display tank, which can result in stilted flow patterns, dead spots, and a more intrusive look.

The current trend in the hobby is toward low-profile external overflow boxes, as these take up little space inside of your display, and contain all of the plumbing on the outside of your tank.

A couple of quick terms that you will hear bandied about a lot in this hobby:

  • Weir– A german word, a weir is a low dam usually built across a river.  But in our hobby, a weir is the dam that separates the display tank water from the overflow box.
  • Surface Skimming- surface skimming is the process of removing proteins and organics from the surface of the water by means of cascading into an overflow box.  This helps keep the surface of the water clean, and is pretty much the only way water enters into the overflow box in the saltwater hobby.

If you were to just have a single drain pipe in your overflow box, it would likely make loud siphon sucking sounds. Not only that, if it were to ever get clogged, you would quickly have a saltwater mess on your hands.  So currently, in the saltwater hobby, we primarily rely on one of three overflow methods.

a) Durso Method

© Marine Depot

Not my preferred method, the Durso Standpipe relies on a single drain which can lead to clogging issues.

The Durso method works by using a durso standpipe, which is basically a piece of PVC with a U-shaped fitting on the top and an air vent hole. The intake line is downward facing and below the water line in the overflow box.  The goal of the Durso Method is to create a silent overflow system, and when tuned and installed correctly, it does accomplish that goal.

b) Herbie Method

Herbie Style Overflow Diagram
© Marine Depot

The Herbie overflow method is my preferred overflow system, primarily because it has an emergency drain, plus the primary drain is adjustable by means of a gate valve.

In order to install a Herbie style overflow system, you need three separate bulkheads: the primary drain, the emergency drain, and the return.

The Herbie method achieves a silent overflow by means of maintaining a constant water height above the level of the primary overflow, but below the emergency overflow.  This water height is achieved by adjusting a gate valve to fine tune the level.

c) Bean Animal Method

infographic of bean animal style filtration system
© Marine Depot

The Bean Animal Method is a hybrid of the Durso and Herbie methods.  It consists of a primary drain which utilizes the Herbie method, a secondary drain which is a Durso Standpipe, and a tertiary drain which is the emergency overflow.

This is probably the best method for achieving a silent overflow while being able to accommodate large volumes of water. But the downside is most tanks don’t come pre-drilled with space for four bulkheads, which means you will either have to externally plumb the return lines, or drill a fourth hole for the return.

2) Soft Plumbing

Soft plumbing uses flexible tubing to transport water to and from your display tank.  It is the most simple and cost effective way to plumb your tank. There isn’t a whole lot to talk about, so let’s just briefly go over what you need to know:

a) Vinyl Tubing

6 feet clear flexible tubing on white background

Vinyl tubing is probably the most common in the saltwater hobby.  It is super easy to find, inexpensive, and can be picked up at any hardware store.  It comes in various colors, so choose one that fits your aesthetic needs best!

b) Braided Tubing

Braided tubing is basically vinyl tubing with a lot of reinforcements.  It is meant for high pressure applications, and costs more.  For 99% of hobbyists, braided tubing will not be necessary, as simple and inexpensive vinyl tubing will be more than enough!

c) Silicone Tubing

More expensive than vinyl tubing, I rarely use silicone tubing. If for some reason I have a super noisy pump, I’ll often use a piece of silicone on it because it does not transfer the vibration nearly as much as vinyl tubing.

d) RO Tubing

Polyethylene tubing, more commonly known as RO tubing, is commonly used in home RO drinking water systems, and in RO/DI filters for the saltwater aquarium hobby.  Great for RO/DI filters, ATO systems, and two-part dosing.

e) Airline Tubing

It’s always good to have a bunch of airline tubing lying around.  Super useful, great for drip acclimation, running a battery powered air stone in case of emergency, or using for two-part dosing.  Inexpensive, I’d recommend having a pack on hand!

f) Connections


For flexible tubing, there really are 2 types of connections, barbed and push.  You don’t really have a choice in which one to get, as most pieces of equipment make the decision for you.  When plumbing your drains and return pumps, you will use a barbed fitting.  When using an RO/DI filter, you will use push fittings.  And when using a media reactor, it just depends!

g) Hose Clamps

five plastic hose clamps on white background
Plastic Hose Clamps
Metal Hose Clamp

For flexible tubing, there really are 2 types of connections, barbed and push.  You don’t really have a choice in which one to get, as most pieces of equipment make the decision for you.  When plumbing your drains and return pumps, you will use a barbed fitting.  When using an RO/DI filter, you will use push fittings.  And when using a media reactor, it just depends!

3) Hard Plumbing

There is a lot more to talk about when it comes to hard plumbing.  Let’s get the basics out of the way first.  Hard plumbing uses PVC, which is hard, hence the term, hard plumbing!

Have you ever wondered what PVC stands for, well here you go! Polyvinyl chloride… it is a synthetic thermoplastic material made by polymerizing vinyl chloride… So basically, it is some type of hard plastic!  

This blog is not meant to be a “how-to” on hard plumbing, but rather an overview of terms so you can at least get an understanding.

If this is your first saltwater aquarium and you are like me and not a great plumber, I would consider buying a reef style tank that comes with a sump and pre-fabricated plumbing, rather than designing and building your own.  Here’ are a couple great tanks that fit that bill.

Waterbox Reef 70.2 Plus
Red Sea Reef Deluxe XL 200

a) Schedule 40/80

Schedule 40
Schedule 80

PVC pipes and fittings come in either schedule 40 or schedule 80.  Schedule 40 is almost always white, while schedule 80 is almost always grey.  Schedule 40 is thinner, less expensive, easier to find, and meant for low pressure plumbing such as the saltwater aquarium.

Schedule 80 on the other hand is much more difficult to find (especially the fittings), and is meant for high pressure situations not commonly found in this hobby.

I usually use schedule 80 in my plumbing just because the color is so much more attractive than the white schedule 40!

There are some online retailers that sell different colors of schedule 40, so just look around.

b) Cement/Primer

In order to securely attach pieces of PVC together, you need to use a combination of primer and cement.  Wear gloves, goggles, and a mask, as this stuff is stinky…

Also, for professional plumbers, they are required to use a purple primer. That way when the building inspector comes in, they can prove they used primer.  But in the saltwater hobby we don’t want purple primer, because it just doesn’t look good on the final product.  So I’d recommend getting the clear primer above.  It can be a bit tricky to find at your local hardware store, but any plumbing store should carry it.

One quick note… When you are connecting PVC to your ABS bulkhead, don’t use the above primer and cement.  You have to use a special ABS to PVC transition cement like the one below.

c) Slip/Thread


Pretty obvious what the difference is.  Slip fittings require primer and cement to hold together, while threaded fittings just screw together, but often need some sort of o-ring or plumber’s tape to make a water-tight seal.

d) Valves

Alright, so let’s give a super quick overview of that various valves out there, and then I’ll have links to all of them below.

  • Gate Valve– These have an interior gate that goes up and down.  Great when you need to be able to precisely control the amount of flow.
  • Ball Valve– Probably the most widely used valve in this hobby, you cannot fine-tune it as much as a gate valve, but perfect for most applications.
  • Check Valve– Generally used on the return pump line to stop the display tank water from overflowing your sump in case of a power outage.
  • Float Valve– Often used in auto top off settings or RO/DI filter setups.
Gate Valve
Ball Valve
Check Valve
Float Valve

e) Fittings

So a super quick overview of the most common fittings out there, with pictures below.

  • Adaptors- Threaded to slip, PVC to hose barb, male to female, an adaptor takes two separate types of PVC fittings and connects them together.
  • Bushings- used to connect two different sizes of PVC together, so either reducing or increasing the diameter of the pipe.
  • Elbows- 90° or 45°, these turn your plumbing.
  • Tees & Wyes- when you need to split your plumbing from one to two.
  • Unions- used in places where you want to be able to easily remove part of your plumbing.
  • Bulkheads– creates a water tight seal between the wet and dry side of your aquarium, for example in between the display tank and the cabinet.
  • Couplers- join together two pieces of PVC that are the same size.
1" black pvc bulkhead on white background

IV) Sumps

A sump is a container that holds water, usually housed directly below your display tank.  A sump serves many functions:

  • It increases the overall water volume of your tank which helps stabilize swings in water parameters.
  • It is a place to hide all of your equipment.
  • And it allows for greater filtration because you can house more equipment than either a HOB or rear filtration system.

Let’s take a peek at the MD Elite Sump and talk about the various stages.

Marine Depot Elite Sump by Trigger Systems

The Marine Depot Elite Sump comes in both a 30″ and 36″ version, and they are made by Trigger systems, arguably one of the most noted names in the custom acrylic sump game! (I know that seems like a super specific market, but amongst hobbyists it’s a big deal!)

Let me just say, I love this sump!  I have a different custom acrylic sump in my 120 gallon, which I love by the way.  But the attention to detail given to this MD Elite Sump is exquisite.  Here are some of the features:

  • 100% acrylic and made in the good ol’ USA.
  • 7″ filter sock with drip plate.
  • 4x probe holders of various sizes.
  • 2x cable organizers.
  • Adjustable baffle to control water height in skimmer compartment.
  • Bubble trap with two layers of filtration perfect for media bags.
  • 5x 1/4″ quick disconnect fittings great for ATO pumps and/or dosing pumps.
  • 3.5 gallon configurable chamber perfect for an ATO reservoir or refugium setup.

Stages of a Sump

© Marine Depot

While there are different styles of sumps out there, the MD Elite probably has the most common type of layout.

  • Stage 01- the drain silencing chamber is where water first enters your sump, and is meant to reduce bubbles and provide a quiet place for the water to land.
  • Stage 02: The filter sock chamber is the first step in your mechanical filtration.  You can either put filters socks in here, or you could put a media cup and fill it with filter floss or some sort of sponge media.
  • Stage 03: The largest chamber is usually a place for your protein skimmer, but it is also a great location for media reactors and probes.
  • Stage 04: The bubble trap is meant to reduce the amount of micro bubbles that your skimmer produces, before entering the return chamber.  The bubble chamber on the MD Elite is also a media chamber because it comes with two levels perfect for media bags.
  • Stage 05: The return chamber is where you put your return pump.  In the MD Elite sump it is also a place for you heater.
  • Stage 06: The configurable chamber is meant for either your ATO reservoir, or to be setup as a refugium.

Obviously different sumps will set things up a bit differently, but the essence is the same.

VI) Episode 10: Maintenance

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