How to Lower Phosphates in the Aquarium


There are a lot of benefits in having an aquarium at home. Aside from being an elegant and sophisticated piece, it has tons of health benefits. A fine aquarium reduces stress levels, increases focus and creativity, and it decreases anxiety. Reasons for having an aquarium are endless.

The benefits of having an aquarium comes along with a price –that is maintaining and regular cleaning. Considerations like how to keep it healthy and how to lower phosphates in the aquarium come along with experience. Here’s a guide on how to keep phosphate levels at bay to maintain the optimum health of your tank.

Where Does Phosphates Come From?

As fishes are confined in an aquarium, they release their waste products in the same environment they live. These waste products are not concentrated on phosphate alone, however, they also become a dominant toxin if an aquarium isn’t regularly cleaned.

Waste products from fishes, uneaten food, and decaying plants gradually produce a breakdown of products that ultimately become phosphate. It is a decompositional by-product of wastes in general. Other sources of phosphates include:

  • The tap water
  • Decaying algae
  • Dead fish
  • Aquarium salts
  • pH buffers
  • Carbon filter media

How to Lower Phosphates in the Aquarium?

There are a lot of ways in lowering down the phosphates levels in an aquarium. But the best way in keeping these phosphate levels at a minimum is by preventing its rise. This is done by regularly checking its levels and doing maintenance routines.

Consider these ways on lowering down phosphate levels to keep your aquarium in a healthy state.

Changing water

Changing your aquarium water often has a lot of benefits. Aside from lowering down the phosphate levels, it also keeps the other toxins at bay. However, this solution is temporary. Unless the root of the rising phosphate level is addressed, phosphate will still increase.

You may check the water that you regularly use in your aquarium as some cities have significant phosphate levels in their tap. Distilled or filtered water is an alternative to ensure that phosphate levels are low.

Cleaning the tank

It is a no-brainer that cleaning your tank regularly can lower down phosphate levels. Cleaning the inside walls, the decorative pieces, rocks, and fake plants gets rid of algae that contributes to increasing phosphate levels. Do not forget to clean the filter media.

Placing aquatic plants

Naturally placing aquatic plants significantly reduce phosphate levels. These plants grow fast and they feed on nitrates and phosphates. The addition of aquatic plants also provide a healthier environment for your fish as they can be another source of oxygen and a playful hiding spot.

Altering the feeding strategy

Uneaten food is a source of phosphate that is preventable. Overfeeding your fish can lead to a higher water load. It is best to only feed your aquatic pets an amount that they can consume at a given period.

Removing leftovers is a good way to decrease phosphate levels. Thaw the frozen fish food as it can also contain higher levels of phosphates. You can also opt to change brands as some have higher phosphate content than others.

Use of phosphate removers

The use of chemicals should be your last resort as it can alter the water composition of your tank. These removers are commonly chemical filter media that are placed in the aquarium with a high water flow. It then binds the phosphate in the flowing water.

How Phosphates Levels Affect Aquarium Fish?

Phosphate is a very reactive substance that is easily absorbed by aquarium fish. Although it does not directly cause toxicity, phosphate levels should be kept low in an aquarium.

If these phosphate levels continually rise, it can cause harm to the health and vigor of your fishes and plants. Allowing phosphate levels to rise contributes to growth of algae. When algae dominate your aquarium, they compete for oxygen supply with the other living things inside.

This can starve your fish with the oxygen that they need daily.

Frequently Asked Questions


How to Test Phosphates in Aquarium? 

Testing for phosphates in your aquarium is a valid routine to keep its amounts low. There are a lot of phosphate testing kits that can help you monitor its levels. Instructions on each test kit depends on the brand.

Most test kits will require you to take a sample of aquarium water and add the test kit. You will have to compare the color of the water tested with the color card that usually comes with the test kit.

How often should Aquariums be tested for Phosphates?

Testing for phosphate content is usually done weekly. It is reasonable to check for the level of phosphate at this rate because it can cause algae growth rapidly. Phosphate is generally a natural substance that occurs in a fish tank, and its nontoxic levels can also be of great benefit for the corals. Thus, it is important to keep phosphates at a safe level.

What Level of Phosphates in Aquarium is Safe?

Phosphates that are too low can also starve the corals. While high phosphate content can inhibit coral calcification and promote algae growth. The safe level of phosphate is below 0.02 ppm. Some aquarium enthusiasts and reefers give an allowance of 0.05 to 0.07 ppm as the ceiling value.

Poorly maintained aquariums can have phosphate levels as high as 5 ppm. This level can deplete your fish of its oxygen levels. With this phosphate content, algae can become a lush pasture dominating your tank.


The beauty and health of your aquarium lies in how much you are willing to do maintenance and cleaning. The awareness of how to lower phosphates in the aquarium gives you an advantage of keeping your fish, plants, and corals at their best state.

Phosphates aren’t villains in the aquarium that you should totally defeat. It is rather a substance that you need to control to maintain the ecosystem of your fish healthy and in great shape. Phosphates can aid in coral growth at minimum levels. Preventing this level to rise at the dangerous side is the challenge you should conquer.

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