Posted on / by Dr. Moshe Harel / in Global Application

Fish-Ponds Treatment with Lake Guard™ Blue

Place:    People’s Republic of China, Hunan province, Changde

Date:     July 30 – Aug. 5, 2019


The purpose of the pilot was to demonstrate the advantages of the use of Lake Guard™ Blue as an economic, safe and environmental mean to control harmful algal blooms in aquaculture.

The pilot included 3 fish ponds: one (#B5-5 @ 2,500 m2) serving as a treated control; the second (#B5-6 @ 2,500 m2), was prescribed with a single, aggressive, dose in order to achieve an immediate result in terms of reducing bloom levels; the third (#B4-6 @ 5,000 m2) was treated conservatively, over 3 consecutive days in order to achieve maximal results without dramatically impacting the life in the pond.

Description of Application:

Both ponds #B5-5 and #B5-6 were dosed on July 30, 2019.

#B5-6 was aggressively treated at 10 am with a single dose of 5kg Lake Guard™ Blue (20kg/ha.), applied manually from the bank of pond. The particles of the Lake Guard™ Blue traveled with the currents and the wind across the pond, interacting with the phytoplankton inhabiting the water surface. Application time lasted under 5 min.

#B5-5 was treated on the same day in the hours of the afternoon with 4 kg (16kg/ha.) copper sulfate pentahydrate. The application was done from banks around the pond and lasted half an hour. The granules applied into the water sank to the bottom upon impact.

#B4-6 was dosed with 1kg Lake Guard™ Blue on Aug. 2 (2kg/ha.), 1.5kg Lake Guard™ Blue on Aug 3 (3kg/ha.) and 2.5kg Lake Guard™ Blue on Aug. 3 (5kg/ha.) – altogether, 10kg/ha.

On Aug. 1, a single fish kill was observed in Pond #B5-6, which was treated 48 hours earlier with 5kg Lake Guard™ Blue. This common phenomenon is attributed to the immediate collapse of the cyanobacterial population in the pond as a result of the treatment, the release of significant quantities of toxins into the water and the increased levels of heterotrophic bacteria that fed on cyanobacterial dead cells, hence deteriorating DO levels in the water. In response, pond management diluted the water in pond #B5-6 by a ratio of ~1:5 with cyanobacterial-contaminated water from an adjunct pond.

The significant results in the pond, presented hereunder, are in spite of these actions.

Sampling methodology:

Throughout the pilot period quantitative measurements were made by YSI ProDSS probe, measuring Dissolved Oxygen, pH, Chlorophyll-a, and Phycocyanin (PC). Chl-a measurements serve as a proxy for total algal biomass in the water. PC levels serve as a direct proxy to total cyanobacteria biomass in the water.

At the same time, qualitative assessments were made visually.


  1. Change in Cyanobacterial and Total Algal Levels (Fig. 1A-B):

Prior to treatment (at time 0), #B5-6 had PC values of 15.63 µg/l and Chl-a values of 47.00 µg/l. 72h into the pilot, PC concentration dropped to 2.40 µg/l (-85% from time 0) and Chl-a concentration increased to 65.00 µg/l (138% from time 0). By the end of the pilot, PC values increased to 4.85 µg/l (-69% from time 0) and Chl-a concentration increased to 139.67 µg/l (297% from time 0).

Prior to treatment (at time 0), #B5-5 had PC values of 16.89 µg/l and Chl-a values of 32.56 µg/l. 72h into the pilot, PC concentration dropped to 8.9 µg/l (-48% from time 0) and Chl-a concentration increased to 79.00 µg/l (242% from time 0). By the end of the pilot, PC values increased to 10.93 µg/l (-35% from time 0) and Chl-a concentration decreased to 61.00 µg/l (187% from time 0).

Prior to treatment (at time 0), #B4-6 had PC values of 6.12 µg/l and Chl-a values of 60.18 µg/l. By the end of the pilot (72), PC values dropped to 3.67 µg/l (-41% from time 0) and Chl-a concentration increased to 90.11 µg/l (150% from time 0).


2 Severe blooms of predominantly cyanobacteria species were treated with Lake Guard™ Blue in aquaculture fishponds.

The simple treatment “surgically” removed the dominant species and enabled other nontoxic phytoplankton species to thrive in the ecological niche. This happened through a “Killing the Winner” mechanism that enables natural competitors to occupy the ecological niche and contribute to the lasting effect of the treatment.

Chl-a values represent the concentration of all photosynthetic organisms (cyanoabcteria as well as non-toxic green alage). PC values represent only cyanobacterial concentrations.

The ratio between these values expresses the composition of these two population species in the Pond. Under healthy conditions, this ratio should be in favor of non-toxic species that serve both as a valuable nutrient in fish ponds, as well as a biological, natural, buffer that prolongs the effect of the treatment and prevents cyanobacterial species from reestablishing themselves.

It serves to evaluate the pond’s “Resistance Factor” to cyanobacterial blooms.

Over the course of the pilot, the Chl-a/PC ratio in pond #B5-6, which was treated with Lake Guard™ Blue improved by 957%.

During the same time, tin The total change in the Control pond, #B5-5 improved by a total of 289%.

In pond #B4-6 where the duration of treatment was shorter, the increase was to 250% (Fig. 2).

When further examining the trends of the ‘Resistance Factor’ over time, the quality of the treatment with Lake Guard™ Blue is further enhanced:

While the treatment in the Control pond, (#B5-5) achieved a limited immediate impact on the Resistance Factor, this effect was short living and kept deteriorating on a daily-basis.

At the same time, the aggressive treatment in pond #B4-6 dramatically imporoved the said Resistance Factor, which remained constant throughout the rest of the trial. Pond #B4-5, on the other hand having been treated more conservatively, with lower doses, showed healthy incremental increases in th ratio between nontoxic and toxic species, without the adverse effects associated with a sudden collapse of a bloom.

The significance of the ‘Resistance Factor’ to pond management and its impact on the the pond’s health clearely correpond with the situation on the ground, as it was clear to the naked eye thorughout the pilot (Fig. 3).

These results are in agreement with an ongoing work done in Israel and the US over 100s of ponds ranging from 5-150 ha.

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