Water is more than 70% of the Earth's surface. There are currently about 220,000 known marine species. Aquariums are therefore designed to allow people to visit and learn more about marine species. The public's awareness in the protection of marine life has improved as time increases. Thus, more aquariums and Ocean parks are opening up all over the world. However, all aquariums are struggling with a single cleaning problem. In the aquarium, workers need to clean the aquarium tanks regularly to remove the biofilm layer. Biofilm is a layer of bacteria that binds together and is embedded in the extracellular substance that they secrete. Including polysaccharides, lipids, proteins and DNA. Biofilm naturally grows in aquarium tanks; however, excess biofilm can be a particular concern to large aquariums. Accumulation of biofilm consumes a lot of oxygen, at the same time suffocating the nitrifying bacteria. It also benefits other aquatic organisms’ growth such as algae, which is unwanted in aquarium because more algae will consume more oxygen and therefore reduces the quality of the water.
Due to the rapid growth of biofilm, cleaning has to be done regularly, especially frequently for large aquariums. Currently, biofilm is generally removed by scraping-off with a brush.However, some biofilm is able to attach tightly on rough surfaces. In order to remove this kind of biofilm, cleaners are required to put on extra effort and time to fully remove it, which is very time and manpower consuming.
Fig 1. The diver is scraping biofilm off using brush, shot in Chimelong ocean Kingdom.
Moreover, some aquatic creatures in the aquarium tank are very fragile, such as corals and jellyfish, etc. When dealing with corals, biofilm can't be removed if the force is too soft. But too much force will also damage the coral. Jellyfish are very sensitive to bubbles. When the cleaners dive into the water, some air bubbles will be generated. Jellyfishes are unable to remove air bubbles inside their body. Once air bubbles are absorbed. It could die from absorbing too much air bubbles. In addition, cleaners maybe hurt by other aquatic creatures in the tanks. For example, aggressive sharks may attack the cleaners, and toxins released by jellyfishes can also make people allergic. These are all the reasons that increase the difficulty of biofilm cleaning.
The difficulty with current cleaning method?
In order to deepen our understanding in the actual situation and the difficulty in cleaning. We went to visit the Chimelong Ocean Kingdom, one of the most famous Ocean Parks in Zhuhai, Guangdong Province in China. There we communicated with one of the workers responsible for aquarium cleaning, Mr. East. When asked about the difficulties they are facing with, Mr. East said that apart from consuming manpower and material resources, underwater cleaning itself is a work that requires good physical fitness. Water pressure increases as the size of water depth of the large fish tank increases. Staying under a high-water pressure environment for a period of time could be a burden on human body. In small aquarium tanks, where some tiny aquatic creatures are displayed. The corners and crevices of smaller tanks are difficult to reach and clean.
Since the removal of biofilms is a large issue for aquariums and ocean parks around the world. Our team was inspired to apply synthetic biology to society in order to develop an efficient biofilm removal model called Biofilm-Removing E. Aquarium Cleaning Coli (BREAC). This is accomplished by the engineering of bacteria to express the adhesive protein to be bound to biofilm, and the digestive enzyme to biodegrade biofilm. In addition , based on the feedbacks from stakeholders. We optimized our concept with two systems: a light-inducing system and a magnetic-removing system. With these two systems, our bacteria can degrade biofilm safely without accumulating in water and reducing the quality of the water.
Fig 2. The physical application of BREAC.
Success of our project will have a cheap and low-labor biofilm removal model that can be used in aquariums around the world, from small fish shops to large ocean parks.
- Biofilm in our aquarium. How to remove? Retrieved from https://aquariumbreeder.com/biofilm-in-our-aquariums-how-to-remove/