Refugium Setup Tips For Nitrate And Phosphate Control

Grow algae to stop algae...perplexing, isn’t it? When it comes to refugiums for your reef tank that is exactly the idea and this episode of the 5 Minute Saltwater Aquarium Guide will show you exactly how it works and why you should consider the lazy reefers approach to nutrient removal for your tank.

Chaetomorpha in large sump refugium

Why Do I Need a Refugium?

A refugium is a filtration component where we intentionally grow certain forms of algae or plants to naturally uptake pollutants from the tank. It’s not shiny or or fancy but it is one of the coolest and, arguably, one of the most effective ways to deal with excess nitrate and phosphate that can build up in a reef tank.

During later stages of the tank, somewhere around 2 - 3 years and beyond, pest algae and slime that feed on excess phosphate and nitrate are just not as common as they are during the first 12 months when they are very common.

Algae growing in a reef tank

There are a variety of reasons why that first year is more challenging including experience with managing feeding, filtration and maintenance. One of the biggest reasons, however, is mature tanks typically have larger, growing corals that uptake a majority of that excess nitrate and phosphate. Coralline algae coverage, various microfauna and clean up crew critters will typically also be well established, all of which will help reduce the build-up of nitrate and phosphate.

There are a variety of ways to control nitrates and phosphates during the first 12 months with things like small frequent water changes, conservative feeding, chemical and mechanical filter media and even some highly effective bacterial solutions.

None of that, however, is as easy as walking by a refugium and removing a handful of Chaeto taking the locked-up nutrients along with it. Plus, once you get a refugium growing it is difficult to mess up.

Hang-on refugium with chaetomorpha

How A Refugium Works

The way this works is the excess food and fish waste in the tank eventually breaks down into excess nitrate and phosphate. These compounds are plant fertilizers that when combined with light, will promote algae growth.

Rather than growing pest algae in the display tank, the idea is to grow really easy to harvest macroalgae in an isolated filtration compartment called a refugium to consume those extra nutrients. In some cases, this can be so effective that a refugium is capable of stripping the water of near all traces of nutrients but that can easily be avoided.


CPR AquaFuge

We are going to skip a refugium for the Red Sea E170 and utilize a hang-on style refugium on the 40 breeder. There really isn't a super clean and easy way to add a refugium to the Red Sea all in one tank without reconfiguring the filtration and adding a sump down below.

CPR Aquafuge on 40 Breeder aquarium

The 40 breeder lends itself nicely to hang-on equipment like the CPR Aquafuge. Yes, we will agree hang-on gear is not all that attractive, it can be bulky and unsightly. With your first tank, the inside of the tank is more important than the outside. In other words, don’t focus on the form factor as much as the function. A refugium is going to drastically increase your success rate and really help you to get through the first 12 months.

With that in mind, a refugium is optional and you do not need to have one if it violates your aesthetic goals for the tank. Exactly the reason we chose to not use a refugium on the Red Sea E170.

Adding macroalgae to a hang-on refugium

The medium size CPR AquaFuge covers about half of the back of the tank. You could probably get away with a smaller one but the medium size refugium matches the light setup we plan to use quite well.

Refugium Lighting

CPR sells an optional light designed to set on top of the AquaFuges but the mount is not very secure and the spectrum is not optimized for macroalgae growth.

Kessil LED Light over refugium

In the last few years, we have seen a refugium evolution around using the proper light spectrum to increase macroalgae growth. This has proven to make refugiums a very effective and viable method of nutrient export, more so than ever before.

We chose the Tunze 8831 Waterproof LED light instead which does have that optimized light spectrum for plant growth and is waterproof so worrying about it falling into the water is not a worry at all. Well worth the extra $20.

Tunze Waterproof Refugium LED Light

The magnetic mount will secure the light to the side or back of the refugium and simply connect it to a classic timer. The light schedule we chose to run will be opposite the tank meaning the refugium will be lit from 7 pm - 7 am. This not only helps maintain a more stable pH but also ensures the refugium does not have to compete with the lights on the front of the tank.

The light schedule is essentially how you will negotiate how much nutrients the refugium removes. Longer light schedules up to 18 hours can be used for maximum nutrient removal while short light schedules down to 6 hours can be employed for minimal removal.

Algaebarn Chaetomorpha packaging

Choosing Macroalgae

There are a variety of different algae you can effectively grow in a refugium but Chaetomorpha (commonly called “Chaeto”) is going to be your best option because it is hardy, grows fast and safe.

You want to start with a clean source from a company that takes pride in minimizing pests and parasites such as AlgaeBarn. Do not get it from a friend’s tank because it is almost certain to come with pests., no sense in learning the hard way.

Algaebarn Live Goods

Refugiums have some additional benefits including increased biodiversity and feeding the tank. Refugiums offer prime conditions for Copepods, Amphipods and various other microfauna to grow and reproduce. These small “pods” are largely considered very beneficial for your aquarium as food for the fish but also help keep things clean and stable.

Red Sea E170 Aquarium

What’s Next

Both of our 40-gallon tanks here at the office are, for the most part, set up. Knowing what to do when things are going smoothly, however, is only half the battle. What about when things take a turn for the worse?

Spotting problems early is going to be the most critical step in avoiding some major disasters and in the final few episodes of our series we are going to show you exactly how to keep yourself out of trouble, beginning with pest or nuisance algae.

5 Minute Saltwater Aquarium Guide Episode #25

Looking for a different topic or have questions? You can binge the entire 5 Minute Saltwater Aquarium Guide playlist right here on our website. We also invite you to join the #askBRStv Facebook Group which is a free resource for you to ask questions, get advice, interact with other hobbyists and get your daily reef aquarium fix.

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