A potential zero water exchange system for recirculating aquarium using a DHS-USB system coupled with ozone

Area of Science:

• Aquatic systems management
• Environmental microbiology
• Water quality engineering

Background:

• Recirculating aquarium systems (RASs) typically rely on partial water exchange, which consumes significant water resources.
• Maintaining optimal water quality and aesthetic appeal in RASs is crucial for aquatic life and system stability.
• Conventional methods often lack sustainability due to high water consumption.

Purpose of the Study:

• To evaluate the efficacy of the ozone-down-flow hanging sponge-up-flow sludge blanket (ozone-DHS-USB) system as a sustainable alternative to water exchange in RASs.
• To assess the impact of ozone application on water quality parameters and microbial communities within the DHS-USB system.
• To determine the system's ability to maintain safe nitrogen concentrations and reduce organic compounds.

Main Methods:

• The ozone-DHS-USB system was integrated into a freshwater aquarium and operated under fluctuating ambient temperatures (23°C–34°C).
• Water quality parameters, including color, ammonia, and nitrate levels, were monitored throughout the experimental period.
• Microbial community analysis was performed using 16S rRNA gene sequencing to assess changes in bacterial populations, particularly nitrite-oxidizing bacteria (NOB).

Main Results:

• The ozone-DHS-USB system effectively maintained water color below 10 color units during ozonation phases.
• Ammonia and nitrite levels were consistently kept below 0.1 mg N L⁻¹, and nitrate levels averaged 14.6 ± 9.20 mg N L⁻¹.
• While ozone application led to a decrease in NOB, carp survived for 425 days without any water exchange, indicating system viability.

Conclusions:

• The ozone-DHS-USB system demonstrates significant potential for creating low-maintenance aquaria by eliminating the need for water exchange.
• The system effectively manages key water quality parameters, ensuring the health and survival of aquatic organisms.
• Further research into optimizing ozone dosage and its long-term effects on microbial ecosystems is warranted.