Product Overview

Remove Phosphorus. Restore Water Quality.

Phoslock is emerging as the best new technology for reducing phosphorus in ponds, lakes and reservoirs.

  • Patented Phosphorus Locking Technology
  • Rapid & Permanent Removal of Phosphorus
  • Total Maximum Daily Load (TMDL) Compliance Solution
  • Water Quality Restoration

Phoslock is a patented phosphorus locking technology to restore water quality in ponds, lakes and reservoirs. Phoslock was developed by the Australian national science agency, Commonwealth Scientific and Industrial Research Organization (CSIRO), to remove phosphorus from water bodies and restore water quality. For over ten years, Phoslock has been successfully used in water resource restoration programs around the world. Although Phoslock is a new technology to the United States (2010), it is rapidly emerging as the most effective phosphorus inactivation and water quality restoration solution for ponds, lakes and reservoirs.

Given the favorable features of Phoslock, such as its very low toxicity, its ability to permanently bind free reactive phosphorus (FRP) over a wide range of water chemistries, and the fact that it does not form flocs, Phoslock is emerging as the most effective phosphorus locking technology for in-situ phosphorus management in surface water.

How Phoslock Works

For more information about Phoslock and assistance in developing a water quality restoration program, contact your SePRO Aquatic Specialist or call 1-800-419-7779, or by e-mail,

Labels and SDS

Specimen Label

Safety Data Sheet

Phoslock Case Studies

Water Quality Restoration of a Phosphorus Impaired Florida Lake

Similar to many other lakes in Florida and around the United States, Pine Lake has been plagued by eutrophication caused by excessive phosphorus accumulation. Listed as phosphorus impaired by the Florida Department of Environmental Protection, Pine Lake required mitigation restore water quality.

Full Case Study (PDF)

Water Quality Restoration in Laguna Niguel Lake

Phoslock provided the water resource managers and public who enjoy Laguna Niguel Lake an ecologically sound in situ solution to address phosphorus pollution and restore water quality.

Full Case Study (PDF)

Lake Lorene

AquaTechnex, LLC biologists along with Twin Lake HOA concluded the excess phosphorus concentrations in Lake Lorene needed to be reduced in order to improve water quality. The recommended in‐situ approach for Lake Lorene was the application of the phosphorus locking technology Phoslock (applied June 2012). Monitoring was conducted throughout the season resulting in a 53% reduction in free reactive phosphorus(FRP), a 40% reduction in total phosphorus 4 months after application. The reduction of in water phosphorus concentrations in Lake Lorene demonstrated the ability of Phoslock initially inactivate FRP in the water column, immediately bind available phosphorus in the sediments and break the cycling of phosphorus in the lake.

Full Case Study (PDF)

Crooked Stick Golf Club (2011)

SePRO Corporation, in partnership with Crooked Stick Golf Club, Indiana, initiated a phosphorus mitigation program with Phoslock on June 23, 2011. The objective of the project was to reduce phosphorus levels and restore water quality in this pond. Total phosphorus level were measured at 182 ppb prior to application, dropped 58% to 76 ppb within 48 hours following application and two months later remained at levels 70% lower than pre-applications conditions.

Full Case Study (PDF)

1st U.S. Phoslock Application, California (2010)

Mason Lake, California had chronic water quality issues impacting the health and enjoyment of the waterbody. The lake management firm AquaTechnex selected the proactive solution of Phoslock to address the high levels of phosphorus (water & sediment) and reset the eutrophication clock of this lake. The Phoslock application resulted in a 45% reduction in total phosphorus one month after application, a reduction of ortho-phosphorus below limits of detection for 4 months following application and improved water clarity by 4 feet. This first operational application in the United States confirmed the international successes of Phoslock programs and demonstrated the impressive ability of this patented technology to bind phosphorus and restore water quality.

Full Case Study (PDF)

Silbersee, Germany (2009)

The Silbersee is a recreational lake near the German city of Bremen which was treated with Phoslock in November 2006. The lake was one of the first lakes in Germany to be treated with Phoslock and consequently is one of the earliest European case studies. Prior to the application had been regularly closed to recreational users during the summer months due to high internal phosphorus load in the lake and poor water quality. The aim of the application was therefore to reduce this internal phosphorus load and restore water quality. Since the application, phosphorus levels have been reduced significantly and the lake has remained open to recreational users without interruption. A small re-application of Phoslock was undertaken in November 2009 to capture new inputs of phosphorus.

Full Case Study (PDF)

Het Groene Eiland, Netherlands  (2009)

The lake at the “Het Groene Eiland” camping park near the town of Appeltern in the Netherlands.  The aim of the Phoslock application was to remove 110 kg and 31 kg of phosphorus from the available nutrient pool of both the water column and the releasable fraction of the sediment for the entire lake.  The lake was treated with Phoslock on the 16th and 17th of April 2008.   A planned low does second application was applied on the 31st of March 2009 to bind phosphorus unaccounted for in the first application.   The application of Phoslock to “Het Groene Eiland” has reduced the overall phosphorus levels and restore water quality.  The lake has remained open for recreational use without interruption since the application of Phoslock.

Full Case Study (PDF)

Clatto Phoslock Report, Scotland (2009)

Clatto Reservoir is a former drinking water supply reservoir located on the outskirts of the city of Dundee in Scotland. In recent years, the reservoir has been used for a variety of recreational purposes, excessive phosphorus pollution has resulted in the reservoir to be closed for extended periods of time due to concerns about public health and safety. Keen to find a solution to this problem, the Dundee City Council commissioned an application of Phoslock in March 2009. The objective of the application was to remove the immediately and potentially available phosphorus from both the water column and sediments of the reservoir. The results of the application have been impressive and in 2009 the reservoir remained open to the public for the first time in several years during the peak summer period of June to August.

Full Case Study (PDF)

Barensee, Germany  (2008)

The Bärensee is a popular lake used for swimming and fishing which is located within the largest camping area in the Federal German State of Hessen. Phoslock was applied to the lake on 12 and 13 June 2007 to bind phosphate in the water column and prevent phosphorus release from sediments. The application was performed by Bentophos GmbH, the licensee for Phoslock in Germany. In the six months following the treatment, total phosphorus levels dropped from 84 µg/L to 25 µg/L. In the three years since the application, the lake has remained open to swimmers water quality has been restored.

Full Case Study (PDF)

Phoslock Trial in Canning River, Australia  (2001)

The applications of Phoslock on impounded sections of the Canning and Vasse Rivers in 2000 and 2001 by the Western Australian Water and Rivers Commission, the Swan River Trust and CSIRO Land and Water were the first full scale applications of Phoslock and were undertaken as trials during the development of Phoslock to determine whether the application of Phoslock could significantly reduce phosphorus in the water column and sediments of these rivers. The applications resulted in reductions in phosphorus concentrations in the water column to below detection limits and substantial reductions in phosphorus efflux from sediments during the course of the trials.

Full Case Study (PDF)

If an algae bloom is present, treat with a SePRO algaecide prior to a Phoslock application. Phoslock is a registered trademark of Phoslock Water Solutions Ltd.

Technical Information

Phoslock is a modified bentonite clay product containing lanthanum, a naturally occurring earth element. Several independent organizations have conducted extensive laboratory and field studies on the toxicity of Phoslock using a range of aquatic organisms and the United States Environmental Protection Agency toxicity testing criteria. The results of acute and chronic toxicity tests of Phoslock and lanthanum using a number of sensitive organisms including: several species of water flea (Daphnia); several species of Rainbow fish; freshwater shrimp; benthic organisms such as amphipods, mayflies and midge larvae; demonstrated no toxicity of Phoslock to aquatic organisms at the dose rates used to remove FRP from surface waters.

The possibility of direct exposure of Phoslock and/or lanthanum to the human body is very limited during or after an application of Phoslock. We suggest that there is no risk to human health by a Phoslock application to a water body (including drinking water reservoirs) at dose rates used to remove FRP from surface waters. The safety margin is substantial and sufficient to ensure that the only exposure of lanthanum (in Phoslock) would always be much less than the therapeutic dose used in the medical industry. Handlers and applicators should always follow label and MSDS directions.

The following reports summarizes Phoslock and lanthanum technical information, and a number of toxicity studies conducted by private and government agencies to assess the performance and potential risks associated with the use of Phoslock in natural aquatic environments.

The Problem with Phosphorus

Phosphorus enrichment of water bodies negatively impacts water quality. The accumulation and internal recycling of phosphorus in water bodies have significant and lasting impacts on the aquatic ecosystem, drinking water supplies, and recreational uses. Also, excessive phosphorus levels can result in regulatory implications due to exceeding of total maximum daily load (TMDL) thresholds and state and/or federal water quality standards.

For more information on the impact and problems associated with excessive phosphorus levels in the water, visit the following links:

Watershed Management Isn’t Enough

Proactive watershed assessment and management actions are important best management practices to reduce the level of phosphorus entering water bodies. Even when external sources of phosphorus have been curtailed by watershed management practices, the internal recycling of phosphorus in water bodies can continue to degrade water quality and have lasting impacts on the aquatic ecosystem. 'In-Lake' phosphorus mitigation is a critical component of an integrated approach to restore impaired water bodies.

Application of Phoslock

Phoslock is applied either as a granule or slurry through customized application equipment. Please contact SePRO for guidance on the proper application method and equipment for your Phoslock project.

Phoslock Application (High Volume Surface Spray)

Experts in Aquatic Solutions

SePRO’s Technical Specialists are trained to assist you with your toughest issues, from aquatic weeds that keep coming back to nusiance or toxic algae that are plaguing a water body. See how we can help.