The Ruby Tetra (Axelrodia riesei) stands out as one of the most captivating micro fish in the aquarium hobby. Despite their diminutive size of just 0.8 inches, these South American gems display a stunning ruby-red coloration that catches the eye of any aquarist. I've kept these fascinating little fish for several years, and their unique combination of vibrant color and peaceful nature makes them perfect for nano aquarium enthusiasts.
Native to the Rio Meta basin in Colombia, Ruby Tetras inhabit slow-moving blackwater streams with dense vegetation and soft, acidic water. Their natural environment provides crucial clues for successful captive care. Unlike their more common cousins in the types of tetra fish family, Ruby Tetras require specific attention to water chemistry and tank setup to truly thrive.
What makes Ruby Tetras particularly special is their suitability for nano aquariums. In an era where smaller living spaces drive the popularity of compact aquarium setups, these tiny fish offer maximum visual impact in minimal space. Their care requirements, while specific, aren't overly demanding once you understand their needs.
Species Overview and Natural Habitat
Ruby Tetras belong to the genus Axelrodia, which contains only four recognized species. Scientific classification places them in the family Characidae, making them true tetras despite their miniature size. First described in 1960, these fish have remained somewhat rare in the aquarium trade, adding to their appeal among collectors.
In their natural habitat, Ruby Tetras inhabit waters with temperatures ranging from 75-82°F (24-28°C) and pH levels between 4.5 and 6.5. The Rio Meta basin where they originate features heavily tannin-stained water from decomposing leaf litter, creating the characteristic blackwater conditions these fish prefer. Water flow in their native streams remains gentle, with dense stands of aquatic plants and overhanging vegetation providing cover from predators.
The fish display sexual dimorphism, with males showing more intense red coloration and slightly slimmer bodies compared to females. Adult Ruby Tetras reach a maximum size of 0.8 inches (2 cm), making them one of the smallest tetra species available in the hobby. Their lifespan in captivity typically ranges from 3-5 years with proper care.
Understanding their natural ecology helps explain their behavior in aquariums. Ruby Tetras are micropredators, feeding on tiny invertebrates and zooplankton in the wild. They're also schooling fish, naturally occurring in groups of dozens or even hundreds, which influences their social requirements in captivity.
Tank Setup Requirements
Setting up an aquarium for Ruby Tetras requires careful attention to their specific needs. While they're small fish, they still need adequate swimming space and proper environmental conditions to display natural behaviors and vibrant coloration.
Tank Size and Dimensions
A minimum tank size of 10 gallons works for a small school of 8-10 Ruby Tetras. However, I recommend a 15-20 gallon long tank for optimal results. The horizontal swimming space matters more than height, as these fish occupy the middle and upper water columns. A tank with dimensions of 24" x 12" x 12" provides an ideal footprint for a Ruby Tetra biotope setup.
For nano tank enthusiasts, a well-maintained 5-gallon tank can house 6-8 Ruby Tetras, but this requires diligent maintenance and stable water parameters. Remember that smaller water volumes experience more rapid parameter fluctuations, which can stress these sensitive fish.
Filtration and Water Flow
Ruby Tetras require gentle water flow that mimics their natural stream habitat. A small sponge filter or a hang-on-back filter with adjustable flow works perfectly. Aim for a turnover rate of 4-5 times the tank volume per hour. Position the filter output to create a gentle current without creating turbulent areas that stress the fish.
Biological filtration is crucial for maintaining the pristine water quality these fish require. Sponge filters excel in this regard, providing both mechanical and biological filtration while creating minimal current. If using a hang-on-back or canister filter, consider adding a pre-filter sponge to prevent these tiny fish from being sucked into the intake.
Substrate and Decoration
Dark substrate enhances the Ruby Tetra's coloration and mimics their natural environment. Fine sand or small, smooth gravel in black or dark brown works best. Avoid sharp or coarse substrates that might damage their delicate fins or mouths when foraging.
Aquascaping should focus on creating a naturalistic environment with plenty of hiding spots. Use driftwood, particularly pieces that release tannins, to help create blackwater conditions. Indian almond leaves, oak leaves, or commercially available botanicals not only stain the water but also provide beneficial compounds that promote fish health.
Plants and Lighting
Live plants play a crucial role in a Ruby Tetra tank. They provide security, help maintain water quality, and create spawning sites. Suitable plants include Java moss, Anubias nana, Cryptocoryne species, and floating plants like Amazon frogbit or Water sprite. These plants thrive in the lower light conditions that Ruby Tetras prefer.
Lighting should be subdued to replicate the dappled sunlight of their natural habitat. Use a timer to maintain a consistent 8-10 hour photoperiod. LED lights with adjustable intensity work well, allowing you to find the sweet spot between plant growth and fish comfort. Floating plants help diffuse bright lighting while providing additional cover.
Water Parameters and Conditions
Maintaining stable water parameters is perhaps the most critical aspect of Ruby Tetra care. These fish have evolved in specific conditions, and deviations can lead to stress, disease, and shortened lifespans. Understanding proper aquarium water chemistry becomes essential for their long-term success.
Essential Water Parameters
Parameter | Ideal Range | Acceptable Range | Notes |
---|---|---|---|
Temperature | 77-80°F (25-27°C) | 75-82°F (24-28°C) | Stable temperature crucial |
pH | 5.0-6.0 | 4.5-6.5 | Acidic water essential |
GH (General Hardness) | 1-4 dGH | 0-6 dGH | Very soft water required |
KH (Carbonate Hardness) | 0-2 dKH | 0-3 dKH | Low buffering capacity |
Ammonia | 0 ppm | 0 ppm | Zero tolerance |
Nitrite | 0 ppm | 0 ppm | Zero tolerance |
Nitrate | <10 ppm | <20 ppm | Keep as low as possible |
Creating Blackwater Conditions
Ruby Tetras thrive in blackwater conditions that replicate their natural habitat. Several methods exist for creating these conditions in your aquarium. The simplest involves adding botanicals like Indian almond leaves, alder cones, or oak leaves directly to the tank. These materials release tannins and humic acids that lower pH, provide antibacterial properties, and tint the water a tea-like color.
Commercial blackwater extracts offer a more controlled approach to achieving desired water conditions. Products containing concentrated tannins allow precise dosing without the decomposing organic matter that botanicals introduce. Start with half the recommended dose and adjust based on your water's response and visual preference.
Peat filtration provides another effective method for creating soft, acidic water. Adding peat to your filter media slowly releases acids that lower pH and soften water. However, this method requires careful monitoring as the acidifying effect diminishes over time, necessitating regular peat replacement.
Water Change Schedule
Regular water changes maintain the pristine conditions Ruby Tetras require. I perform 20-30% water changes weekly, using aged or RO water matched to tank parameters. The low bioload of these small fish means water changes focus more on removing accumulated organics and replenishing minerals than diluting nitrogenous waste.
When performing water changes, match the replacement water's temperature and pH to avoid shocking the fish. Pre-treating water with blackwater extract or allowing it to sit with botanicals for 24 hours helps achieve consistent parameters. Always use a quality water conditioner to neutralize chlorine and chloramines.
Diet and Feeding Requirements
Ruby Tetras are micropredators with small mouths requiring appropriately sized foods. In nature, they feed on tiny invertebrates, insect larvae, and zooplankton. Replicating this varied diet in captivity ensures optimal health, coloration, and breeding success.
Primary Diet Components
High-quality micro pellets or crushed flakes form the dietary foundation for Ruby Tetras. Look for foods specifically formulated for small tropical fish, with a protein content of 40-50%. The food particles must be small enough for their tiny mouths – generally under 0.5mm in diameter. I've found that crushing regular tropical flakes between your fingers creates appropriately sized particles.
Live foods trigger natural hunting behaviors and provide excellent nutrition. Baby brine shrimp, microworms, and vinegar eels are perfectly sized for Ruby Tetras. Daphnia and cyclops also work well, though larger specimens may need crushing. Culturing these foods at home ensures a constant supply and reduces feeding costs.
Frozen foods offer convenience while maintaining nutritional value. Frozen baby brine shrimp, cyclops, and daphnia are readily available at most aquarium stores. Thaw small portions in tank water before feeding to prevent digestive issues. Some Ruby Tetras initially refuse frozen foods but typically accept them after a few offerings.
Feeding Schedule and Techniques
Feed Ruby Tetras small amounts 2-3 times daily rather than one large feeding. Their small stomachs and high metabolism benefit from frequent, small meals. Offer only what they can consume in 2-3 minutes, removing uneaten food to maintain water quality.
These shy fish may not compete well with aggressive feeders, so observe feeding sessions to ensure all fish receive adequate nutrition. Creating multiple feeding zones by releasing food at different tank locations helps ensure even distribution. Some aquarists use feeding rings to concentrate food in specific areas, making it easier for Ruby Tetras to feed without competition.
Supplemental Feeding
Variety prevents nutritional deficiencies and maintains interest in food. Supplement the primary diet with treats like freeze-dried bloodworms (crushed to size), spirulina flakes, and color-enhancing foods containing carotenoids. These supplements should comprise no more than 20% of the total diet.
Consider adding infusoria or green water cultures to the tank occasionally. These microscopic organisms provide natural grazing opportunities and supplement the diet with live prey. This becomes particularly important when conditioning fish for breeding or raising fry.
Tank Mates and Compatibility
Selecting appropriate tank mates for Ruby Tetras requires careful consideration of their small size, peaceful nature, and specific water requirements. Not all fish that tolerate soft, acidic water make suitable companions for these tiny tetras.
Ideal Tank Mates
Other micro fish species make the best companions for Ruby Tetras. Ember Tetras, Green Neon Tetras, and Celestial Pearl Danios share similar size and temperament. These species won't outcompete Ruby Tetras for food and create a harmonious community. The pristella tetra guide shows another peaceful species that works well in similar water conditions, though they're slightly larger.
Small Corydoras species like C. pygmaeus or C. habrosus make excellent bottom-dwelling companions. They occupy different tank levels, reducing competition, and their peaceful nature poses no threat to Ruby Tetras. Otocinclus catfish also work well, helping control algae while remaining completely peaceful.
Dwarf shrimp species, particularly Cherry Shrimp and Crystal Red Shrimp, coexist peacefully with Ruby Tetras. The shrimp help clean up uneaten food while adding visual interest to the lower tank levels. However, Ruby Tetras may eat shrimplets, so provide dense plant cover for breeding shrimp populations.
Tank Mates to Avoid
Avoid keeping Ruby Tetras with any fish large enough to eat them. This includes most cichlids, larger tetras, and predatory species. Even peaceful larger fish like Angelfish pose a threat once they reach adult size. The stress of living with potential predators significantly impacts Ruby Tetra health and coloration.
Aggressive or fin-nipping species should never share a tank with Ruby Tetras. Tiger Barbs, Serpae Tetras, and even some smaller barbs may harass these peaceful fish. Similarly, fast-swimming, boisterous species like Zebra Danios can stress Ruby Tetras and outcompete them for food.
While Betta fish might seem compatible due to their preference for similar water conditions, results vary greatly depending on the individual Betta's temperament. Some Bettas ignore Ruby Tetras completely, while others may chase or attack them. If attempting this combination, have a backup plan ready.
Species-Only Setup Benefits
Many aquarists find that Ruby Tetras display best in species-only setups. Without competition from other species, they become bolder, show better coloration, and exhibit more natural behaviors. A group of 15-20 Ruby Tetras in a planted 20-gallon long creates a stunning display that rivals any community tank.
Species-only setups also simplify care requirements. You can optimize water parameters specifically for Ruby Tetras without compromising for other species' needs. Feeding becomes easier when all fish have the same dietary requirements and feeding behaviors.
Breeding Ruby Tetras
Breeding Ruby Tetras presents a rewarding challenge for dedicated aquarists. While not impossible, successful breeding requires attention to detail and proper setup. Their small size and specific requirements make raising fry particularly challenging.
Breeding Setup and Conditioning
A separate breeding tank of 5-10 gallons works best for controlled breeding attempts. Set up the tank with soft, acidic water (pH 5.0-5.5, GH 1-2) and a temperature of 80-82°F. Use a mature sponge filter for gentle filtration and add fine-leaved plants or spawning mops for egg deposition sites.
Condition breeding pairs with high-quality live and frozen foods for 2-3 weeks before breeding attempts. Feed small amounts multiple times daily, focusing on protein-rich foods like baby brine shrimp and microworms. Watch for females developing fuller bodies indicating egg development and males showing intensified coloration.
Some breeders use rain simulation to trigger spawning. This involves performing a large water change with slightly cooler, softer water to mimic seasonal rainfall in their natural habitat. Gradually increasing feeding and extending photoperiod to 12 hours can also encourage breeding behavior.
Spawning Behavior and Egg Care
Ruby Tetras are egg scatterers that show no parental care. Spawning typically occurs in early morning, with males pursuing females through plants. The female releases 30-50 tiny eggs that stick to plants or fall to the substrate. Adults will eat eggs if given the opportunity, so remove parents immediately after spawning.
The tiny, transparent eggs hatch in 24-36 hours at 80°F. Eggs are extremely sensitive to fungus, so some breeders add methylene blue or alder cones to provide antifungal properties. Maintain stable water parameters and avoid disturbing the breeding tank during this critical period.
Raising Fry
Ruby Tetra fry are among the smallest in the aquarium hobby, requiring microscopic foods initially. Infusoria, paramecium cultures, or commercial liquid fry foods provide first foods for 5-7 days. As fry grow, introduce newly hatched brine shrimp nauplii and microworms.
Maintain pristine water quality through small, frequent water changes using aged water matched to tank parameters. Growth rates vary, but fry typically reach 0.25 inches after 6-8 weeks. At this size, they can eat crushed flakes and join adult Ruby Tetras in the main tank.
Common Health Issues and Prevention
Ruby Tetras, while generally hardy when kept in appropriate conditions, can succumb to various health issues if their specific needs aren't met. Prevention through proper husbandry remains the best approach to maintaining healthy fish.
Stress-Related Conditions
Stress represents the primary health threat to Ruby Tetras. Poor water quality, inappropriate tank mates, or insufficient group size causes chronic stress that weakens their immune system. Stressed fish display faded colors, clamped fins, and reduced activity. They may also hide constantly or refuse food.
Address stress by identifying and correcting the underlying cause. Test water parameters immediately and perform water changes if needed. Ensure the group contains at least 8 individuals and remove any aggressive tank mates. Adding more plants or adjusting lighting can help shy fish feel more secure.
Common Diseases
Ich (white spot disease) occasionally affects Ruby Tetras, particularly newly imported specimens. The characteristic white spots appear on fins and body, accompanied by flashing behavior. Treat with gradual temperature increase to 86°F combined with aquarium salt or commercial ich medications at half strength due to their sensitivity.
Fin rot may develop in fish kept in poor water conditions. Frayed, discolored fins indicate bacterial infection requiring immediate intervention. Improve water quality through increased water changes and treat with antibacterial medications if necessary. Mild cases often resolve with improved husbandry alone.
Neon Tetra Disease, despite its name, can affect Ruby Tetras and other characins. Symptoms include restlessness, loss of coloration, and curved spine. Unfortunately, no cure exists, and affected fish should be humanely euthanized to prevent spread. Quarantine new fish to prevent introduction of this devastating disease.
Preventive Care Measures
Quarantine all new fish for 2-4 weeks before adding them to established tanks. This prevents disease introduction and allows observation for health issues. Maintain a simple quarantine setup with hiding places and stable water parameters matching your main tank.
Regular maintenance prevents most health issues in Ruby Tetras. Weekly water testing catches parameter drift before it becomes problematic. Consistent water changes, filter maintenance, and removal of decomposing matter maintain the pristine conditions these fish require.
Observe your fish daily during feeding for early disease detection. Changes in behavior, appetite, or appearance often indicate developing problems. Early intervention significantly improves treatment success rates.
Seasonal Care Considerations
While aquarium fish live in controlled environments, seasonal changes still affect their care requirements. Understanding these variations helps maintain optimal conditions year-round for your Ruby Tetras.
Summer Care Adjustments
Rising ambient temperatures during summer can push tank temperatures above the ideal range for Ruby Tetras. Monitor temperatures closely and consider adding a fan directed at the water surface or installing a chiller for extreme situations. Increased temperatures accelerate metabolism, so slightly reduce feeding to prevent water quality issues.
Higher temperatures also decrease oxygen solubility in water. Ensure adequate surface agitation for gas exchange and consider adding an air stone if fish show signs of oxygen stress like gasping at the surface. Perform water changes during cooler morning hours to avoid temperature shock.
Winter Maintenance
Heating becomes critical during winter months. Use an appropriately sized, adjustable heater with a reliable thermostat. I recommend using two smaller heaters rather than one large unit for redundancy. If one fails, the other maintains survivable temperatures until you can address the issue.
Reduced daylight during winter may affect both fish and plants. Maintain consistent photoperiods with timer-controlled lighting to prevent disrupting biological rhythms. Some aquarists report better breeding success when mimicking natural seasonal light variations, though this remains largely anecdotal.
Long-Term Care and Aging
As Ruby Tetras age, their care requirements may shift slightly. Understanding these changes helps provide appropriate care throughout their 3-5 year lifespan.
Caring for Senior Fish
Older Ruby Tetras often become less active and may struggle to compete for food with younger, more vigorous tank mates. Consider setting up a retirement tank with gentle filtration and easy food access for elderly fish. Slightly warmer temperatures (78-80°F) can help maintain metabolism in aging fish.
Watch for age-related health issues like decreased appetite, slower swimming, or difficulty maintaining position in the water column. While some decline is natural, sudden changes warrant investigation. Adjust feeding strategies to ensure older fish receive adequate nutrition, perhaps feeding them separately from younger fish.
Maintaining Colony Health
Successful long-term Ruby Tetra keeping involves maintaining a sustainable population. Rather than keeping the same group until they all age out, periodically introduce younger fish to maintain colony dynamics. This provides more natural social structures and ensures continuity if breeding attempts succeed.
Document your care routine, including water parameters, feeding schedules, and any health issues encountered. This record becomes invaluable for troubleshooting problems and refining your husbandry techniques over time. Share successful techniques with other aquarists to contribute to collective knowledge about these remarkable fish.
Troubleshooting Common Problems
Even experienced aquarists encounter challenges with Ruby Tetras. Here are solutions to frequently encountered issues:
Problem: Fish Hiding Constantly
Ruby Tetras hiding indicates stress from various sources. Check group size first – less than 8 individuals causes insecurity. Increase group size to 10-12 for better confidence. Bright lighting also drives hiding behavior; dim lights or add floating plants for shade. Aggressive tank mates, even seemingly peaceful species, may intimidate these tiny fish. Remove any fish causing stress.
Problem: Poor Coloration
Faded colors in Ruby Tetras usually stem from suboptimal conditions. Test water parameters immediately, focusing on pH and hardness. These fish need soft, acidic water for best coloration. Diet also affects color; incorporate color-enhancing foods and varied live foods. Stress from any source causes color loss, so address environmental issues comprehensively.
Problem: Refusing Food
New Ruby Tetras often refuse food initially due to stress. Offer various foods including live baby brine shrimp, which few fish can resist. Try feeding at different times and tank locations. Established fish refusing food indicates illness or water quality issues. Test parameters and observe for disease symptoms. Sometimes crushing food smaller helps fish with mouth injuries or elderly individuals.
Frequently Asked Questions
How many Ruby Tetras should I keep together?
Keep a minimum of 8 Ruby Tetras together, though 10-15 creates a more natural, confident school. In larger groups, they display better coloration, more natural behavior, and reduced stress levels. Single specimens or pairs will be constantly stressed and rarely survive long-term.
Can Ruby Tetras live in hard water?
Ruby Tetras require soft, acidic water to thrive. While they might survive temporarily in moderately hard water, they won't show good coloration, may refuse to breed, and typically have shortened lifespans. Use RO water or peat filtration to achieve appropriate parameters if your tap water is hard.
How can I tell male and female Ruby Tetras apart?
Males display more intense red coloration and have slimmer, more streamlined bodies. Females appear slightly larger and rounder, especially when carrying eggs. During breeding condition, these differences become more pronounced, with males showing their best colors while actively pursuing females.
What's the minimum tank size for Ruby Tetras?
While a 5-gallon tank can technically house 6-8 Ruby Tetras, I recommend a minimum of 10 gallons for better stability and swimming space. A 15-20 gallon long tank provides ideal conditions for a proper school and allows for the aquascaping that makes these fish feel secure.
Do Ruby Tetras eat shrimp?
Adult shrimp coexist peacefully with Ruby Tetras, but newborn shrimplets may be eaten. If breeding shrimp, provide dense moss or plant cover where baby shrimp can hide until they're large enough to avoid predation. Cherry shrimp and Amano shrimp make particularly good tank mates.
How often should I feed Ruby Tetras?
Feed Ruby Tetras small amounts 2-3 times daily. Their small stomachs and high metabolism benefit from frequent, small meals rather than one large feeding. Offer only what they consume in 2-3 minutes and remove uneaten food to maintain water quality.
Can Ruby Tetras live with Bettas?
Success depends entirely on the individual Betta's temperament. Some Bettas ignore Ruby Tetras, while others may chase or attack them. If attempting this combination, introduce Ruby Tetras first, provide plenty of plants for cover, and have a backup plan if aggression occurs.
Why are my Ruby Tetras swimming at the surface?
Surface swimming typically indicates oxygen deficiency or poor water quality. Test ammonia, nitrite, and nitrate immediately. Increase surface agitation for better gas exchange and perform a water change if parameters are off. High temperatures also reduce oxygen solubility, so check your heater settings.
Are Ruby Tetras good for beginners?
Ruby Tetras aren't ideal for absolute beginners due to their specific water requirements and sensitivity to parameter changes. However, aquarists with some experience maintaining soft water fish will find them rewarding. Their care isn't difficult once you understand their needs, but they don't tolerate mistakes well.
How long do Ruby Tetras live?
With proper care, Ruby Tetras typically live 3-5 years in captivity. Optimal water conditions, appropriate diet, and stress-free environment maximize lifespan. Fish kept in suboptimal conditions or subjected to frequent stress may only survive 1-2 years.
Conclusion
Ruby Tetras offer aquarists a unique opportunity to keep one of nature's jewels in miniature form. Their brilliant coloration, peaceful nature, and suitability for nano tanks make them increasingly popular among hobbyists seeking something special. While their care requirements are specific, they're not unreasonably demanding for prepared aquarists.
Success with Ruby Tetras comes from understanding and replicating their natural habitat. Soft, acidic water, gentle filtration, subdued lighting, and appropriate tank mates create an environment where these fish thrive. Regular maintenance and attention to detail prevent most problems before they develop.
The growing interest in nano aquariums and biotope setups positions Ruby Tetras perfectly for modern aquarium keeping. As more aquarists discover these remarkable fish, collective knowledge about their care continues expanding. Whether kept in a species-only nano tank or as part of a carefully planned community, Ruby Tetras reward dedicated aquarists with a display of natural beauty that belies their tiny size.
For those considering Ruby Tetras, take time to properly set up their environment before purchasing fish. Cycle the tank thoroughly, establish appropriate water parameters, and ensure you can maintain the consistent care these fish require. While they may not suit absolute beginners, aquarists ready for a modest challenge will find Ruby Tetras among the most rewarding species in the hobby. Their ruby-red flash through planted tanks creates living art that continues captivating aquarists worldwide.