How to Lower Phosphate in Reef Tank

Phosphate is essential for a saltwater aquarium, and most people overlook it. The bad thing is that high levels of it can prevent your coral from growing its skeleton and fuel large algae blooms.

It’s a good idea to learn about phosphate, such as why you need it and where it comes from. Then, you’ve got to know the right levels for your tank. After that, you’re going to find out how to lower phosphate levels so that your corals flourish.

How Do Phosphates Affect the Reef Tank?

Phosphates are a form of Phosphor compound. They’re like organic salt and are found in every living thing. Since your aquarium is enclosed as an eco-system, the phosphate levels can slowly build up with time if you don’t remove them in some way.

If you allow phosphates to build at higher levels than recommended for your aquarium, they can negatively affect coral growth and increase algae in the tank.

Coral Growth – Once phosphates reach levels over 0.05ppm, it inhibits calcium carbonate in the water. When some corals want to build their skeletons, they need calcium. They can’t get what they need if phosphate levels are too high, so they stop growing and could die.

Algae Growth – Algae loves phosphate, and if it’s in a high quantity in your aquarium, you can see rapid and large algae blooms. They look bad and can be hard to get rid of later.

Where Do Phosphates Come From?

There are three primary sources of phosphates in the aquarium. These include:

Fish Waste – Decaying matter and fish waste release phosphates into the water. If you’ve got a lot of fish in the aquarium, you’re going to have more detritus and excrement. Therefore, you’ve got to maintain everything and remove the waste quickly.

Fish Food – Flaked fish food is high in phosphate. If you tend to over-feed, you’re sure to have increased levels of phosphate with time. Uneaten food breaks down and releases the phosphate.

Poor Quality Water – Well and city water can have phosphates in it. Make sure you filter it effectively or start using distilled water. That way, you’re not putting in more than your marine life need.

Acceptable Phosphate Levels in Reef Tank

In your reef tank, you need to keep the phosphate levels at under 0.05ppm if you only have fish. However, if you’ve got soft and LPS corals, it needs to be at 0.05ppm. Those who use SPS corals should keep the levels at 0.03ppm.

Some phosphate is necessary so that your corals can use it and grow. Don’t go overboard and strip the water of phosphate. This could also cause the coral to have slow growth or die.

6 Ways to Lower Phosphate in Your Reef Tank

Now that you know how much phosphate you need, it’s time to figure out how to lower the levels if your tank has too much. Methods include:

1. Vacuuming the Sand Bed and Water Changes

Your aquarium is enclosed, so the phosphates do build up with time. You’re physically removing this nutrient each time you do a water change. If you use RO/DI filtered water to replace what you’re losing, the phosphate levels should reduce with time.

Since you’re already doing some maintenance here, it’s best to vacuum out the sand bed. This helps to remove uneaten food, detritus, and decaying matter. Scrape the glass to get rid of the gunk, as well.

These two tasks are the most effective ways to get rid of phosphates in the water and remove them. Make sure you’re performing water changes as often as recommended and cleaning the bed.

2. Use a Protein Skimmer

If you have a protein skimmer, make sure that it is clean, the right size, and working efficiently. This is going to keep your phosphate levels low. The skimmer is there to remove any dissolved organic waste.

As you know, waste breaks down and releases the phosphate within. If you allow the skimmer to move the debris into the collection cup and empty it, you’ve removed the materials. They can’t release their phosphates into the water now.

3. Macro-Algae

Algae consume phosphate, so if you’ve got the room, consider adding an Algae Turf Scrubber or a Refugium to the system. This is going to reduce the amount of phosphate.

Growing macro-algae with a Refugium and removing half of the mass is going to get rid of the phosphate in the algae. This process can remove nitrates, too.

Otherwise, you can use an Algae Turf Scrubber. The device cascades the water within the aquarium down to plastic mesh lit by a special bulb. As your algae grow, it consumes the nitrates and phosphates.

Then, you remove the algae and clean the mesh to get it working again. The algae grow again, consume the nitrates and phosphates, and repeat the entire process over and over.

4. Granular Ferric Oxide (GFO)

GFO is a highly popular product for the long-term control of your phosphates. Most people use it early on with their aquarium once they’ve lowered the phosphate level with other methods.

In a sense, GFO is a maintainer product. It works because it absorbs the phosphate compounds and chemically binds them to the Ferric Oxide. The GFO mass gets used up, so the phosphate levels rise. Now, you just remove the GFO media, throw it away, and replace it with a new one.

GFO can clump, so the most efficient method of implementing it is in a reactor. This helps the granules bubble as water starts to flow through it. Once the GFO is used for the long-term, you can wait up to three months before changing it, depending on your aquarium and phosphate needs.

5. Aluminum Oxide

If you’ve got a ton of phosphate and want to remove it quickly, consider aluminum oxide. You’ve got to be careful when using it because any rapid changes to the water chemistry can shock the aquarium and kill what’s living inside. The product absorbs the phosphate compounds, binding them to the aluminum oxide, and it works quickly.

Usually, you’ve got to replace it every week, and most people only have to use it once to drop phosphate levels significantly. Then, they can use other methods of maintaining it so that it doesn’t get out of control.

Aluminum oxide doesn’t clump like GFO. Therefore, you can put it in a mesh bag and add it to the aquarium or sump until it’s done its job. Ultimately, this product lowers the phosphate first, and then you can use GFO to maintain it and keep phosphates at the right level.

6. Liquid Phosphate Removers

There are various products out there that can chemically attract the phosphates and bind them to the product. Then, you can easily get it out of the water. Options can include UltraLif Reef Liquid Phosphate, Brightwell Phosphate-E, and Blue Life Phosphate Rx.

The liquid binding agent mixes with the phosphate and becomes a solid. Then, the protein skimmer or filtration system collects it, and you can remove it.

Conclusion

Ultimately, the key takeaway here is to keep your phosphates low from the beginning. It takes a multi-angled approach to get it in line, but then it should be easier to maintain the system.

Make sure you’re following good maintenance practices and using a quality filtration system. Try any or all of these methods to see what works for you.