Understanding Refugiums

Refugiums are often talked about when it comes to using a sump. But what is a refugium? Do you really need one? What are the benefits? These are a few of the topics we will hit on in this article that’s all about refugiums!

What is a refugium?

Simply put a refugium is an area, typically part of the sump system, where you can grow algae and give different types of pods a safe place to reproduce away from predators. You can customize the refugium based on what type of algae you want to grow. Some grow better in sand and some grow on rocks.

How to run a refugium

Running a refugium is quite simple if you already have a sump. A common design of sumps is to have three chambers, like shown below.

A sump design with a middle return

While the order of the three chambers can differ, this is the example I use because my sump is set up this way. I have another article all about sumps I’ll include the link here.
The arrows show how the water moves. It gets poured into chamber 1 where typically the protein skimmer goes and moves into chamber 2. This is where the return pump is on my sump and has the variable water level. A T connection sends some of the return water into the third chamber which I like to use as a refugium but can be used for other things too.

Besides having an available sump chamber, you need a couple other things for an active refugium. You need some type of algae and a light for the algae. Chaetomorpha algae is common due to the growth rate and the fact that it never really goes into a reproductive mode releasing plant cells all over the tank. Caulerpa algae is another type grown as it typically grows faster than Chaeto but it does have the tendency to “go sexual” in the aquarium.

Caulerpa algae. Photo from Tampa Bay Saltwater

Lights are a simple thing to get. A simple reflector from Home Depot and a 26w CFL bulb can grow algae. An alternative is thanks to the advances in LED lighting to get a small plant based LED. These are typically very red in the light spectrum although my light shines a very bright purple into my tank stand.

Benefits of refugiums

There are a few mains benefits. Perhaps the biggest is having algae grow in your refugium can prevent algae growing elsewhere in your aquarium. Algae also consumes nitrates and phosphates, keeping them in check for your display tank. By setting your refugium light to turn on when your display tank light is off, you can neutralize the PH in your tank as well. Different types of pods love to eat algae and can reproduce in the refugium to later be introduced to the main tank. With all these benefits it’s no wonder why people run refugiums.

Do you run a refugium in your tank? Why or why not? Comment below!


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