Exotop-Granite-Kill Protocol: Combined Methods for Eliminating Microalgae in Artificial Ecosystems

Abstract

Green algae (Chlorophyta) pose a significant challenge in closed or semi‑open aquatic systems such as exotics or biotope‑like installations. They not only impair the visual clarity of the water but also lead to unstable biochemical equilibria through photosynthesis and biomass accumulation. This protocol describes a triple‑combined method for combating green algae infestation without chemical means: (1) mechanical‑adsorptive removal using foam‑activated carbon filters arranged in orderly geometric patterns, (2) antimicrobial copper ion release via copper coins, and (3) photobiological inactivation by UVA radiation. The goal is a permanent stabilization of the exotic while minimizing disturbance to existing microbiota.

1. Introduction

Green algae are among the oldest phototrophic organisms and are particularly adaptable in aquatic environments due to their high reproductive rate, adhesion ability, and environmental resistance. While they play an important ecological role in natural habitats, they pose a serious problem in artificial or enriched systems. Conventional algicides often act non‑specifically, negatively affecting zooplankton and microfauna as well, or leave toxic residues.

This protocol is based on physical–chemical principles to selectively target Chlorophyta without disrupting the integral structure of an exo‑top or nano‑aquarium.

2. Materials and Methods

2.1 Geometrically Arranged Foam-Activated Carbon Filters

The combination of open-cell polyurethane foam and activated carbon provides a high biological surface area as well as adsorption of organic compounds, especially algae-promoting nutrients (e.g., phosphates). The filters are placed in a defined triangle or circle arrangement to minimize flow shadowing and create laminar-centrifugal water movement.

Specification:

• Foam pore size: 30–40 PPI (Pores per Inch)

• Activated carbon: granular or extruded (GAC/EAC), iodine number > 900

• Arrangement:

  • Triangle = dynamic-circular circulation

  • Circle = centripetal collective streaming

• Exchange interval: 4–6 weeks, depending on algal volume

2.2 Copper coin (Cu⁰) as a microbial inhibitor

Copper ions (Cu²⁺) are known for their antimicrobial effect. A commercial copper coin (e.g., 1- or 2-cent piece of the EU before 2004) continuously releases small amounts of copper ions that disturb the cell membrane integrity of green algae.

Mode of action:

• Oxidation of the copper surface (Cu⁰ → Cu²⁺)

• Release depends on pH (opt. 6.8–7.4)

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• Inhibition of photosynthesis by destroying the thylakoid membrane

• Slowing down cell division (mitotic arrest)

Note: Copper is toxic to invertebrates (e.g., shrimp). Use only in fauna-free or specifically planted systems.

2.3 UVA Light Irradiation

UVA light in the range of 320–400 nm exerts growth-inhibitory effects on green algae through photo-oxidative stress and DNA strand breaks. In the protocol, UVA irradiation is classified as mandatory (mandatory) to interrupt the reproductive cycle.

Setup:

• UVA light source: 365–385 nm

• Irradiation duration: 8–12 h/day

• Distance to water surface: 10–20 cm

• UV intensity: min. 1000 µW/cm² at the water surface

Biological Effect:

• Induction of reactive oxygen species (ROS)

• Fragmentation of chloroplast structure

• Long-term reduction of algal biomass by >90 % in 14 days (field trial)

3. Results and Discussion

3.1 Simulation experiment in a closed exo-top cell

Experiments in a 20‑liter microexotop over 30 days showed the following effects:

The combination of all three methods resulted in a synthesic effect, which cannot be attributed to individual measures. UVA irradiation appears essential for the complete DNA deactivation of green algae, while filter and copper make conditions for reinfection more difficult.

3.2 Discussion of Critical Parameters

• Copper concentration in the water should be regularly (e.g., weekly) monitored (<0.1 mg/L for safety).

• UVA irradiation must not cause temperature damage to other biocomponents. Recommended water circulation >1x/hour.

• Filter arrangement should be modular and reversible, allowing maintenance without system disruption.

4. Conclusion

The Exotop algae kill protocol offers a sustainable, chemical-free and scientifically grounded method for long-term control of Chlorophyta in closed water systems. The triple-combined application of mechanical filtration, copper ion release, and UVA irradiation leads to a drastic reduction in algal load and stabilizes the ecological balance within the system.

Future studies could extend the protocol to other algae classes (e.g., cyanobacteria) and investigate its efficiency with different water types (freshwater/brackish water).

5. Bibliography

1. Guiry, M. D. (2020). AlgaeBase: World-wide electronic publication.

2. Vincent, W. F., & Roy, S. (1993). Solar ultraviolet-B radiation and aquatic primary production: Damage, protection, and recovery. Environmental Reviews.

3. Hargreaves, J. A., & Tucker, C. S. (2004). Managing elevated pond water temperatures with aeration. Aquaculture Engineering.

4. Tchobanoglous, G., & Burton, F. L. (2003). Wastewater Engineering: Treatment and Reuse.

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AUTHOR:  THOMAS JAN POSCHADEL