Home Aquarium Research Articles

Current disease treatments for the ornamental pet fish trade and their associated problems

AbstractThe trade in live ornamental fishes to be held as companion animals or displayed in public aquaria has an estimated global annual value of US$15–20 billion. Supply chains for ornamental pet fishes often involve many more parties than for fish farmed as food fishes, and at each stage, fishes are exposed to stressors including handling, confinement, crowding, mechanical disturbance, and poor water quality. If chronic, these stressors can compromise their immune system, making fishes more susceptible to pathogens. Mortality and morbidity from infectious disease can result in considerable welfare impacts and massive economic losses for the industry, and the range of infective agents seen in ornamental species is well documented. However, treating these diseases is not straightforward with practices varying greatly across the trade and with several approaches having unintended consequences, such as the emergence of resistant strains of pathogens. While disease treatments for a handful of fish species (e.g., koi, goldfish) have received focused research attention, for the home aquarium owner, there is an increasing reliance on products based on natural compounds which have received far less scientific attention. This review aims to highlight the gaps in our knowledge surrounding the range of disease treatments used across the ornamental pet fish trade, with a particular focus on freshwater tropical species destined for home aquaria. Consideration is given to the potential problems arising from these treatments, including microbial resistance and effects of treatments themselves on fish health and welfare.

Transversotrema hafniensis n. sp. infection in Poecilia reticulata by cercariae released from Melanoides tuberculata in Denmark

BackgroundExotic and ornamental fish are highly popular companion animals resulting in a significant transcontinental trade of fish, invertebrates and aquatic plants. A major issue is the diseases associated with these organisms, as they have a major impact on health of the fish in both public and private household aquaria. A secondary issue is the trade with these products, which potentially may expand the distribution area and spread a range of diseases to new habitats.ResultsWe here describe how Poecilia reticulata (guppy), produced in a private household aquarium, were invaded by cercariae of an exotic trematode released by imported Melanoides tuberculata snails. The fish presented with severe clinical signs (tremor, flashing, scraping of body against objects). A standard parasitological examination and morphometric identification showed scale pocket infections with a digenean trematode species within the genus Transversotrema. Molecular identification by PCR, sequencing and phylogenetic analyses of a 2646 bp sequence encoding ribosomal RNA (partial 18 S, ITS1, 5.8 S, ITS2, partial 28 S) was performed. The 1107 bp sequence of mitochondrial DNA (cox1) showed that the parasite differed from previously described Transversotrema species in M. tuberculata. Morphometrics of adult and larval specimens of this isolate also differed from previously described freshwater species within the genus. The new species was described and is named after Copenhagen, for its geographic origin.ConclusionsThe genus Transversotrema comprises a range of species, adapted to a microhabitat in scalepockets of teleosts. A combination of morphological and molecular characterization techniques has been shown to provide a good differentiation between species. The fish were not purchased from a pet shop but produced in the home aquarium. This indicated that an infection pressure existed in the aquarium, where the source of infection was found to be exotic intermediate host snails M. tuberculata, which originally were imported and purchased from a pet shop. The potential spread of fish diseases associated with trade of fish and snails to new geographic regions, where climate conditions are favourable, is discussed.

Growth and Oxidative Stress of Clownfish Amphiprion ocellaris Reared at Different Salinities

Aquaculture of ornamental marine fish is often conducted in recirculating aquaculture systems (RAS) using artificial seawater. Considering the cost of salts to produce artificial seawater (salinity 35‰), we investigated the effect of different salinities (5, 15, 25, and 35‰) on survival, growth, and oxidative stress responses of juvenile clownfish Amphiprion ocellaris. All fish died when reared at salinity 5‰, but at all other salinities survival was ≥95% in the other treatment groups. There was no influence of salinity on growth and oxidative stress responses of clownfish reared at salinities 15, 25, and 35‰, except for the activity of glutathione S-transferase (GST) of fish reared at 25‰, which was significantly lower compared to those reared in salinity 35‰. The salinity of home aquariums is usually 35‰, so even though clownfish can be reared in brackish water, they need to be transferred to full strength seawater (35‰) in order to be commercialized. Therefore, we also evaluated the responses of acute transference of fish reared at 15 to salinity 35‰. There were no mortalities associated with acute salinity transference and no oxidative damage was observed either. The total capacity against peroxyl radicals (ACAP) was immediately increased after fish were placed in salinity 35‰, and remained high after 168 h (7 days), helping fish to deal with oxidative threats. In conclusion, it is possible to rear juvenile clownfish at 15‰ without harming growth or inducing oxidative stress, possibly reducing costs of water salinization. They can be transferred from brackish water to salinity 35‰ immediately before going to the retail market, with no mortality or oxidative damage.

A Review of the Industrial Importance, Common Bacterial Diseases, and Zoonotic Risks of Freshwater Aquarium Fish.

Background: The ever-increasing popularity of home aquariums, most often involving freshwater varieties, has exploded in recent years partially due to the Coronavirus pandemic and related to stay-at-home public health precautions for social distancing. With this ever-increasing popularity of aquariums as a hobby, and whether this involves freshwater or marine fish species, a number of important economic, ecological, and public health issues arise for both fish and hobbyists alike. Materials and Methods: This review highlights the history and genesis of aquariums as both a hobby and an important economic factor (industrial, commercial) for many countries on a global basis. Types of aquarium fish are described, and culture conditions leading to homeostasis in aquatic environments are detailed. When these conditions are not met and aquatic systems are out of balance, the disease can result due to stressed fish. Results: Major bacterial diseases associated with freshwater aquarium fish are reviewed, as are potential human infections related to the care and maintenance of home aquaria. Conclusion: Besides, scientific information was also combined with the false facts of hobbyists who tried to identify and treat diseases during an outbreak in the aquarium. Finally, unresolved issues and important misconceptions regarding the field are discussed.

Gonadal neoplasia in Chinese gold barbs (Barbodes semifasciolatus) from a home aquarium.

Gonadal neoplasia in Chinese gold barbs (Barbodes semifasciolatus) from a home aquarium.

Pseudechidna brummeri: An unexpected discovery in the North-East Atlantic raises concerns

Global changes are currently underway, resulting in the discovery and introduction of new species in unexpected locations. One notable case involves the Indo-Pacific species Pseudechidna brummeri, which was observed and captured on film during a nocturnal dive in Portugal.This situation raises the question: How did this species come to inhabit this area? Two primary explanations appear plausible:a)The species may have been introduced through ship ballast water, a common pathway for the unintentional transport of aquatic organisms. Given the proximity of a large port, this possibility gains significance.b)Alternatively, the species could have originated from a home aquarium, a factor that remains poorly understood. The potential for species to escape or be released from aquariums into natural ecosystems is an area that requires further investigation.Another pertinent question to consider is whether there is only one individual of this species or if there are more individuals present?

Scubcutaneous Mycobacterium marinum infection misdiagnosed as sporotrichosis: A case report

Nontuberculous mycobacteria (NTM), are natural inhabitants of natural waters, engineered water systems, and soils. As a consequence of their ubiquitous distribution, humans are surrounded by these opportunistic pathogens. In this report, we describe a case of scubcutaneous Mycobacterium marinum infection associated with home tropical ornamental fish aquaria. A 43-years-old man reported progressively increasing nodules over his left forearm and hand for more than 7 months. Based on NTM culture, pathological examination, identification by gene sequencing and matrix assisted laser desorption ionization time of flight mass spectrometry, the diagnosis of scubcutaneous NTM infection was confirmed. The patient was treated with itraconazole for suspected sporotrichosis over 1 month. The patient was treated with oral doxycycline hydrochloride capsules (200 mg/day) for 5 months, the nodules had resolved. Home aquarium environments may serve as a possible source of mycobacteria infection in urban family.

Beyond Making Sense

Beyond Making Sense

Functional and Structural Biological Methods for Palytoxin Detection

Palytoxin (PLTX) and its analogues are marine polyethers identified in Palythoa and Zoanthus corals, Ostreopsis dinoflagellates, and Trichodesmium cyanobacteria. Humans can be exposed to these toxins by different routes with a series of adverse effects but the most severe risk is associated with poisonings by the consumption of edible marine organisms accumulating these toxins, as occurs in (sub)-tropical areas. In temperate areas, adverse effects ascribed to PLTXs have been recorded after inhalation of marine aerosols and/or cutaneous contact with seawater during Ostreopsis blooms, as well as during cleaning procedures of Palythoa-containing home aquaria. Besides instrumental analytical methods, in the last years a series of alternative or complementary methods based on biological/biochemical tools have been developed for the rapid and specific PLTX detection required for risk assessment. These methods are usually sensitive, cost- and time-effective, and do not require highly specialized operators. Among them, structural immunoassays and functional cell-based assays are reviewed. The availability of specific anti-PLTX antibodies allowed the development of different sensitive structural assays, suitable for its detection also in complex matrices, such as mussels. In addition, knowing the mechanism of PLTX action, a series of functional identification methods has been developed. Despite some of them being limited by matrix effects and specificity issues, biological methods for PLTX detection represent a feasible tool, suitable for rapid screening.

A survey on aquatic animal keeping practices for home aquariums during the COVID-19 pandemic

Human–animal interactions can generate a variety of benefits for the psychological and physiological wellbeing of humans. Therefore, more people may prefer to keep pets (such as aquatic animals) during stressful events, like the COVID-19 pandemic. In this study, an international survey of aquarium keepers was conducted to assess their attitudes toward home aquariums during the COVID-19 pandemic. Over 80% of the respondents, irrespective of gender, age, employment status, number of owned aquariums, or aquarium maintenance experience, confirmed that aquariums have produced stress-relieving benefits during the COVID-19 pandemic. Approximately, one-quarter of home aquarium owners claimed to have bought more than 15 fish and 15 aquatic invertebrates since the beginning of the stay-at-home restrictions. The majority of the respondents confirmed that their aquarium(s) was/were properly maintained during these regulations, particularly compared to the years prior to the COVID-19 pandemic. To some extent, a shortage of supply of live foods affected the maintenance performance of home aquariums.

Microbiomes and Planctomycete diversity in large-scale aquaria habitats.

In commercial large-scale aquaria, controlling levels of nitrogenous compounds is essential for macrofauna health. Naturally occurring bacteria are capable of transforming toxic nitrogen species into their more benign counterparts and play important roles in maintaining aquaria health. Nitrification, the microbially-mediated transformation of ammonium and nitrite to nitrate, is a common and encouraged process for management of both commercial and home aquaria. A potentially competing microbial process that transforms ammonium and nitrite to dinitrogen gas (anaerobic ammonium oxidation [anammox]) is mediated by some bacteria within the phylum Planctomycetes. Anammox has been harnessed for nitrogen removal during wastewater treatment, as the nitrogenous end product is released into the atmosphere rather than in aqueous discharge. Whether anammox bacteria could be similarly utilized in commercial aquaria is an open question. As a first step in assessing the viability of this practice, we (i) characterized microbial communities from water and sand filtration systems for four habitats at the Tennessee Aquarium and (ii) examined the abundance and anammox potential of Planctomycetes using culture-independent approaches. 16S rRNA gene amplicon sequencing revealed distinct, yet stable, microbial communities and the presence of Planctomycetes (~1–15% of library reads) in all sampled habitats. Preliminary metagenomic analyses identified the genetic potential for multiple complete nitrogen metabolism pathways. However, no known genes diagnostic for the anammox reaction were found in this survey. To better understand the diversity of this group of bacteria in these systems, a targeted Planctomycete-specific 16S rRNA gene-based PCR approach was used. This effort recovered amplicons that share <95% 16S rRNA gene sequence identity to previously characterized Planctomycetes, suggesting novel strains within this phylum reside within aquaria.

Unwanted ‘hitchhikers’ of ornamental snails: a case report of digeneans transported via the international pet trade

In the European Union, aquarium pets are organisms intended for closed places (e.g., pet shops, garden ponds, home aquariums). Until April 2021, regulations did not require veterinary inspection of these animals within the EU, although there is a potential risk of such organisms being released into the environment along with their symbiotes or parasites. Currently, a “disease-free” declaration is required, but no aquarium snail pathogen that needs attention in international trade has been included in the list of potential hazards. Here, we intended to check whether molluscs from the pet trade could be a source of parasites. We answered this question by using Anentome helena, a popular commodity in the ornamental pet industry, as a research model. Snail specimens were randomly collected from aquarium pet stocks imported from Bangkok (Thailand) to Warsaw (Poland) in March 2020. In total, three specimens were subjected to histological examination and 27 specimens were autopsied. Histological analysis revealed that one snail was infected with rediae (and the cercariae inside them). Our study is the first to show the presence of digenean larvae in A. helena originating from the ornamental pet industry. The spread of such “hitchhikers” in non-native areas will likely be associated with threats to environmental and public health. Therefore, it is necessary to constantly draw public attention to the possible consequences of releasing ornamental pets into the non-native environment.

Design and Husbandry Considerations for a Containment Level 2 Aquatic Facility.

The greatly increased use of aquatic species to study disease over the past 20 years necessitates understanding their husbandry and housing requirements to optimize research and welfare and to ensure compliance with regulations. To achieve these goals, aquatic systems have expanded from pet shop and home aquaria to research-grade systems incorporating designs and features to increase their robustness, practicality, and flexibility. Moreover, these last decades have seen the increasing use of aquatic animals for infectious disease research using containment level 2 (CL2)/biosafety level 2 pathogens. In this study, we discuss the facility design requirements and modifications, which must be considered for the planning, construction, and use of an aquatic facility for zebrafish infected with CL2 pathogens. These include decontamination of water and equipment, racking and filtration design, personal protective equipment, and husbandry procedures. This guidance is based on our experience in the design and ongoing management of such facilities.

Human Melioidosis Caused by Novel Transmission of Burkholderia pseudomallei from Freshwater Home Aquarium, United States1.

Nearly all cases of melioidosis in the continental United States are related to international travel to areas to which Burkholderia pseudomallei, the bacterium that causes melioidosis, is endemic. We report the diagnosis and clinical course of melioidosis in a patient from the United States who had no international travel history and the public health investigation to determine the source of exposure. We tested environmental samples collected from the patient’s home for B. pseudomallei by PCR and culture. Whole-genome sequencing was conducted on PCR-positive environmental samples, and results were compared with sequences from the patient’s clinical specimen. Three PCR-positive environmental samples, all collected from a freshwater home aquarium that had contained imported tropical fish, were a genetic match to the clinical isolate from the patient. This finding suggests a novel route of exposure and a potential for importation of B. pseudomallei, a select agent, into the United States from disease-endemic areas.

Relieving pressure from coral reefs: Artificial oyster rocks can replace reef rocks used for biological filtration in marine aquariums

Natural reef rocks have been harvested from the wild for decades to supply the marine aquarium trade. These rocks have been used in home aquariums mostly as substrate to safeguard biological filtration, especially for nitrification. Producing artificial rocks can be a sustainable alternative to the harvest of natural reef rocks from the wild, thus promoting coral reefs conservation. Nonetheless, there is a lack of scientific knowledge on standard formula to prepare artificial rocks, as well as on their potential to promote nitrification. The use of oyster shells, a by-product from oysters’ aquaculture, appears as a promising ecological and economic approach to produce artificial live rocks. Thus, we aimed to develop a standard formula to produce artificial rocks made with oyster shells and test its potential use as a substrate for biological filtration in marine aquariums. For that, we prepared artificial oyster rocks with different sized fragments of oyster shells and compared their ability to promote nitrification of ammonium nitrogen with that of natural reef rocks and fragmented oyster shells. The formula was set at 1 g of dried cement (white Portland cement with limestone) per 3.1 g of dried oyster shell fragments. The volume of water used to prepare this mix was set as 50% of the cement weigh. Our results indicate that artificial rocks made with oyster shells and cement display an ability to promote nitrification similar to that of natural reef rocks, promoting a slight decrease in pH and without releasing PO4–P. All treatments with substrate were able to oxidize up to 21 mg.L−1 of TAN (total ammonia nitrogen, initially added in the form of NH4Cl) within a 48-h interval. In other words, it is possible to safely assume that all tested substrates oxidized an average of ∼4.4 ± 0.1 μg of TAN.g−1.h−1. Thus, our results support that artificial rocks made with white Portland cement and oyster shell fragments are a sustainable option to safeguard a suitable biological filtration in marine aquariums.

The effects of interacting with fish in aquariums on human health and well-being: A systematic review.

BackgroundMost research into the health benefits of human-animal interaction has focused on species that interact physically with humans, such as dogs. This may be unsuitable for certain populations for reasons including accessibility and the risk of negative consequences to both the person and the animal. However, some research has associated viewing fish in aquariums with positive well-being outcomes; as there is no physical contact with the animal, this form of interaction carries less risk. At present, little is known about the specific benefits of human-fish interaction.ObjectivesTo explore current evidence relating to the psychological and physiological benefits of interacting with fish in aquariums.MethodsSystematic searches were conducted to identify relevant primary research of any design. All forms of interaction were considered, including keeping fish as companion animals and fish aquarium-based interventions. “Non-live” alternatives, such as videos, were also considered. This review was conducted according to a registered protocol (PROSPERO ID: CRD42018090466).ResultsNineteen studies were included. Two provided tentative evidence that keeping home aquaria is associated with relaxation. The remaining studies involved novel interactions with fish in home or public aquariums. Outcomes relating to anxiety, relaxation and/or physiological stress were commonly assessed; evidence was mixed with both positive and null findings. Preliminary support was found for effects on mood, pain, nutritional intake and body weight, but not loneliness. All studies had methodological issues and risk of bias was either high or unclear.ConclusionsReview findings suggest that interacting with fish in aquariums has the potential to benefit human well-being, although research on this topic is currently limited. Future research should aim to address gaps in the evidence, such as whether and how the type of human-fish interaction can influence well-being outcomes. Researchers should also aim to address the methodological concerns highlighted in this review.

The Art of Aquarium Keeping Communicates Science and Conservation

In technology-driven societies, scientists and educators alike flounder in making science interesting and applicable. Communicating science, defined as communicating scientific facts as well as teaching and using the scientific process, can also be done informally though leisure activities. In this qualitative study, I examined the leisure activity of aquarium keeping and its ability to communicate relative aquatic facts and processes. This study examined aquarium keepers across the United States via interviews, participant observation, and an ongoing analysis of aquarium hobby literature. Thus, this study indicates (1) caring for a home aquarium communicates science latently, (2) over time, latent science communication becomes activated, and (3) long-term aquarium keeping leads to a personal response in science, as well as conservation. In addition, artistic expression and innovation intersect with scientific knowledge and application to create beautiful, biodiverse, ecosystems. Through the process of successfully maintaining an aquarium, continued participation leads to a proficiency in applicable scientific facts, a better understanding of scientific processes, and an improved conservation ethic for aquatic resources. Further, this intersectionality motivates participation by providing new challenges and various forms of satisfaction. The human dimensions of the aquarium hobby and the values of aquarists are important to understand for many purposes, most notably because it encompasses an enormous sample of the American population and is extremely lucrative to those along most of the supply chain. Aquarium keeping is not only a hobby, but because of the relationship between science and art, it can communicate, as well as spark conservation efforts in

Natural habitats uncovered? – Genetic structure of known and newly found localities of the endangered bitterling Pseudorhodeus tanago (Cyprinidae)

Overuse of natural resources by humans is a major threat to biodiversity. Overuse often involves species of economic or esthetic value, and fish are a typical example for a group that is exploited both for economic reasons (for human consumption) and for esthetic reasons (e.g. by aquarists). Pseudorhodeus tanago (Tanaka, 1909) (formerly known as Tanakia tanago) is a small colorful but legally protected (fishing, keeping and transfer are banned) bitterling fish distributed around Tokyo, Japan. Whereas it is critically endangered and more and more habitat loss has occurred, at least four stocks have been newly found during the last decade. To explore whether emergence of these newly found habitats is a consequence of incomplete survey, we genotyped mitochondrial cytochrome b sequence of P. tanago from 17 localities and an illegal home aquarium. Populations known by the past extensive survey (13 localities) showed geographically structured population genetic characteristics. Population-specific haplotypes were common indicating past divergence and bottleneck events. Four (north, {center + west}, south_1, south_2) or five (north, center, west, south_1, south_2) geographic groups were detectable as for these known localities. On the other hand, newly found stocks were polymorphic and showed identical haplotypes from distant known localities. If we assume historical basis of distribution and genetic characteristics of these newly found stocks, it must be a series of unlikely geological events and haplotype sorting. We discuss potential issues posed by these questionable stocks.

Snapper rest where they see best: visually mediated choice behaviour of Australasian snapper (Chrysophrys auratus)

The sensory physiology and behaviour of many fish species are strongly affected by light. This short study demonstrates that in the Australasian snapper (Chrysophrys auratus) absolute light intensity governs visual acuity and also guides preference behaviour, with fish choosing to ‘rest where they see best’. Use of the optomotor response to test visual acuity at four light intensities (0.01, 0.05, 1 and 3 μmol s−1 m2), showed that visual acuity (measured as directional bias) was best at a light intensity of 0.05 μmol s−1 m2 (84.9% directional bias), but weakened at the highest and lowest light intensity (41.1 and 35.3%). When provided with a choice of the same four light environments fish also spent most time in the 0.05 μmol s−1 m2 light environment, while the highest and lowest intensity light environments were usually avoided. Acclimated light intensity (that is daytime light intensity of the home aquarium) was also 0.05 μmol s−1 m2. By selecting an environment where visual function is optimised, C. auratus are also optimising the ability to search for prey and to detect predators. The results are discussed with reference to habitat utilisation and thoughts for trawl fishing practices.

Investigating body patterning in aquarium-raised flamboyant cuttlefish (Metasepia pfefferi).

Cuttlefish are known for their ability to quickly alter their total appearance, or body pattern, to camouflage or to communicate with predators, prey and conspecifics. The body patterns of some species have been extensively documented to gain a better understanding of their behaviors. However, the flamboyant cuttlefish (Metasepia pfefferi) is largely unstudied. Recently, aquarists have been able to breed, house and display M. pfefferi, giving researchers ample opportunities to study their behavior under those conditions. This study aimed to identify the dorsally-visible components of the body patterns used by 5 sexually-mature, freely-behaving, F5 generation M. pfefferi in their home aquarium at The Seas in Epcot at Walt Disney World Resorts®, Lake Buena Vista, FL, USA. Furthermore, we aimed to determine the most probable patterns used by this population of animals and to create a database of components that can be used in future behavioral studies. We found that this population of M. pfefferi use a combination of 7 textural, 14 postural, 7 locomotor and between 42 and 75 chromatic components in their home aquarium. Using maximum likelihood analysis and AutoClass@IJM software, we found that these components combine to generate 11 distinct body patterns. The software was able to sort 98% of the live animal observations into one of the 11 patterns with 90% confidence and 88% of observations with 99% confidence. Unusually for cuttlefish, 8 of the 11 identified patterns contained at least one “traveling” component (i.e., traveling waves or blinking spots) in which the colors on the skin appeared to travel on the animal’s mantle. In other species, these components are generally seen during hunting or aggression, but this population of M. pfefferi uses them frequently during a variety of contexts in their home aquarium. With few published data on the behavior of M. pfefferi in their natural environment, we cannot compare the behavior of the tank-raised individuals in this study to animals in the wild. However, this study provides the groundwork necessary for future studies of M. pfefferi body patterning and behavior.