Best Aquarium Sump Return Pump

October 4, 2022

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If you own an aquarium you are probably familiar with a lot of the equipment needed to keep your fish alive. These components that provide the life support for your livestock can be an eyesore if you are trying to show off your beautiful fish and plants or coral. We spend a lot of time trying to make our tanks look as beautiful as possible, why would we put an ugly black heater right in the middle of it?

Fortunately, there is a better solution!

Best Pumps For...

Basements	Crawlspaces
Outside	Dirty Water
Yard Drainage	Pool Drainage
Septic Tanks	Aquariums

What is an aquarium sump?

If you have the space and money you can easily add a sump into your aquarium system! An aquarium sump is a separate container that can often be hidden away that holds additional water to be treated and heated and then pumped back into the main display tank. An aquarium sump can be as simple as just adding an additional fish tank in the stand below or as complex as a multi-chambered specifically designed sump that could even be plumbed in a separate room.

Many aquarium enthusiasts use a sump that is hidden away so they can conceal their ugly equipment like heaters, filters, and skimmers. The other advantage is that you can add more volume to the water in your system which helps to buffer the water and prevent the water parameters from changing too rapidly. Many home-aquariums use a sump which is about 20% of the display volume, so if you have a 100-gallon display tank then a 20-gallon pump is an appropriate size, though you could always go bigger if you can afford it!

An aquarium sump pump is used to return the water from the sump back into the main display, and a device named an overflow is used to bring water from the display down to the sump. This guide will help to make sure you choose the correct sump pump for your application.

Pump Size recommendations

Choosing the correctly sized pump for your tank is important, and depends on a lot of different variables. There are a lot of considerations when you are choosing the correct size for your return pump, but often it is much simpler to just consider the pump’s turnover. The turnover is just the volume of water that a pump can move over a period of time, usually measured in gallons-per-hour or GPH. In a freshwater tank the general recommendation is to have a 4x turnover or more, so if you have a 10 gallon tank then you want to make sure your sump is able to move the whole water volume four time per hour, so a pump that can push 40 GPH is a good size. On a saltwater tank the common recommendation is to use a 6x to 10x turnover, so in a 40 gallon tank you will want a return pump that can move between 240 and 400 GPH.

One important thing to watch out for when you are planning your return pump are the head pressure and maximum vertical height. If you need to return water by pushing it directly upwards against gravity you will want to have an idea of how long that plumbing will need to be and buy a pump which can pump that high. You’ll find that most pumps state a maximum height they will pump water up a straight line, if you need to move water up by 6 feet to get back to the display tank, make sure you buy a return pump which is able to do at least 6 vertical feet; probably it’s even better to add some additional feed as a buffer. Over time the pump will tend to get dirty and have degraded performance so it’s best practice to buy a pump that can do 20% more than what you will require.

A final important consideration to take into account is the livestock you will be keeping and their sensitivity to flow. For an example in a freshwater tank, if you have many small and fast-moving fish, like Tiger Barbs or Danios, they could be perfectly suited to a higher flow rate; but if you are keeping a slow moving fish like a pea puffer or angel fish they may prefer their water to be more stagnant and have less flow. Similarly, for saltwater and coral reef tanks, considering what your inhabitants are suited for will help to determine the amount of flow into the tank you will want to have.

Type of pump

There are a variety of different technologies used to pump water, though in the aquarium hobby only two are commonly used: AC pumps and DC pumps.

AC pumps will take the electricity directly from your wall to move a propeller inside the pump that pushes the water to the output. These pumps are usually cheaper so it’s easier on your wallet, but they are also often louder than their DC counterparts. Usually some sound and vibration dampening is ideal for these pumps, which could be rubber feet or suction cups or even setting the pump on top of a rubber pad to prevent the vibrations from carrying through the sump. An AC pump will always run at the same speed so if you do want to have variable control over the flow rate it will have to be done in your plumbing instead of electrically, so for example installing a tee with a gate-valve to return some of the water back into the sump.

A DC pump will often be much quieter than an AC pump, but it will also be more expensive for the same flow rates. One other nice advantage is the DC pump is electronically controllable, meaning you can dial in the exact flow rate you wish to achieve. This can be great in situations where you might want to have a variable amount of flow or have creatures that are sensitive to high flow rates. I like to turn temporarily turn the flow rate up when I am cleaning and doing water changes so that the water gets clearer faster and it helps to kick up more detritus than I would have otherwise cleaned out. Another great thing about DC pumps designed for aquarium sumps is they will have a “feed mode” which will temporarily turn the flow off for usually 10 minutes so that you can feed the aquarium at no flow to make sure all the food gets eaten.

Plumbing the pump

As a final consideration, once you have picked out a pump you like check to find out what size hose barbs it will come with so you know what size hose and other plumbing parts to purchase. Usually hose and hosing parts are measured by their inner diameter (also referred to as an ID). So, if your pump comes with a ½” hose barb then you’ll want to purchase ½” hose to attach to it. A hose with a bigger diameter will be able to move more water faster than a smaller diameter hose, so most times you will want to select the biggest hose possible. Don’t forget to plan to put some ball valves in your plumbing line in case you’d like to shut off the pump without getting water back-flowing into the sump, because a siphon will be created once there is nothing pushing the water up your hose. A check valve can also help with reducing this or you could just drill or make a hole near the outlet up in your display tank to break the siphon.

If you do want to have the ability to control how much flow the pump is producing you may want to consider getting a gate valve and also possibly some tees. The gate valve could be installed directly after the pump if you want, or you could redirect some amount of water back into the sump and change that amount of water using a gate valve.

Finally, it is important to avoid using metal parts in your aquarium to prevent the accidental introduction of heavy metals into your water column. The best option is to always use plastic or nylon in your aquarium plumbing, especially food-grade and parts that say they are meant for an aquarium. If you find no choice but to use metal, make sure it is either titanium or stainless steel 316; other metals have the possibility to erode and contain toxic metals like copper or lead.