September 10, 2025

From the desk of the Founder

I see so many lists of aquatic items that I thought I would devote this issue to my various lists as well.  The most common for people to create seems to be endless lists of favorite fish for a given purpose, like 5 favorite fish for a community tank, the 5 best fish to start an aquarium and such. I can easily do either, but for today I am going to soothe my own peculiar interests and make a list of my 5 favorite fish to keep.

I admit it will be quite eclectic, and ranges over a wide variety of difficulties and habitats.

Appistogramma ramierez - has changed its name lots, but this was what I first knew it as.  The Gold Ram was the first Cichlid I came into contact with way back in the mid 70's.  Cichlids from around the world were just beginning to become available in Canada and the Gold Ram, an offshoot of the German Blue Ram was suddenly available for sale.  I got a few of them to try out, and fell in love with them, so much so, my internet identify is often BlueRam.  

I had some success with breeding livebearers and such for years, but the Gold Ram was the first cichlid I was able to spawn and grow out.  They are fascinating to keep, are rather timid so fit well with small sized community fish.  If they are not threatened they will often pair off, show their spawning colors and rituals and find and protect a place to spawn

Pseudotropheus elongatus (mbuna in general) - The next type of fish that I found was the sudden influx of mbuna (African Rift lake cichlids from Lake Malawi),  The first specimens that appeared were Pseudotrpheus Zebra and Pseudotropheus tropheops which, in the original native colors made an active tank of flashing blue black and orange.  

I soon had a few tanks of Africans, but suddenly a new species was introduced called the Pseudotropheus elongatus.  This is another blue and black barred sleek fish that is like a torpedo in shape.  The advantage of African Cichlids from Malawi is that they are often more comfortable in high density.  A properly set up aquarium with lots of rockwork that provides multiple hiding spaces and tunnels can create multi-generational populations. 

The Pseudotropheus elongatus is an aggressive species and often becomes king of the aquarium as it grows comfortable in the habitat.  Like most other Africans they should be added in groups of 6 or so, since the ratio between males and females is about that for males (1) vs females (5).   

Plecostomus is a group of bottom fish that encompasses a wide range of types within it.  Mainly, the Plecostomus is a generic term covering a wide variety of armored suckermouth catfish - including the Hypostomus, Ancistrus, Hypancistrus, Pterygoplichthys, etc..  There are hundreds of species included under this umbrella, but when I was first introduced to them, early on, they were all simply known as Plecostomus.  They are so ugly they are cute, but what is also so endearing is the amount of cleaning work they perform.

Plecostomus of most species are sold as juveniles, and are so often mislabeled that you really rarely know what you are getting.  There are dwarf species, but they are mostly larger fish, growing up to a foot and over.  They live a long time and grow large, often outgrowing their tank over time. The armoring they have protects them from most other fish so they are quite hardy. They are only rarely aggressive, so can be used in many different environments. The only problem can be placing Plecostomus species in acid water.  They are most comfortable in alkaline water above pH 7.0.  When the water is acid, a problem called acidosis can occur.  The fish often turn white as it dies.   

Zebra Danio - Danio rerio is a small, upper level schooling danio that is a very active passive community fish.  I have always found these are a fish of preference to begin a new aquarium.  They are extremely hardy and easy to spawn, but not in a standard passive community aquarium.  They have been a powerful test species for assorted scientific studies.

The Zebra Danio is a schooling fish that should be kept in groups of at least 5 in od numbers.  They are egg scatters that spawn and then forget the results. Without protection other residents of a community aquarium, so to breed them separate spawning aquariums are required to allow the spawning to occur then they should be removed while the eggs mature.

Niger trigger - Odonus niger is not a freshwater fish, but in the past I have kept salt water fish in marine tanks to understand the differences in style and method.  I like aggressive fish in my tanks, so it is always a challenge to balance an aquarium system.  When you are starting a standard marine aquarium, most people are trying for a coral habitat with peaceful fish in a mainly symbiotic system.  In years past, this was extremely difficult since proper lighting has only become economically viable in the very recent past. Up until that time, the chances of being successful with corals was very low. 

Due to that, In my early years where I was willing to spend the money on marine systems, I went mostly with fish only habitats.  I like the shape and the coloration of the Niger trigger and that they are very hardy.   There are really cheap starter fish to mature the same biological filtration bacteria bed, the cheapest is the black molly.  But, for me in a marine tank, mollies are boring.  The Niger trigger is a hardy and interesting fish to watch in an otherwise bare tank.  

I prefer to keep freshwater fish that are less impacted by sudden changes in their environment.  As a novice aquarist, I would never suggest you try to go into a marine aquarium system.    Unless you are particularly entranced by corals, you can find the colors and activity of African Cichlid tank - You'll never get spawning occurring in a marine tank, but you can easily get multi generational populations in a very active living picture of an African aquarium.

Best Regards,

Steve Pond

Tropical Fish Aquarist

Zebra Danio (Danio rerio)

The zebra danio, scientifically known as Danio rerio, belongs to the family Cyprinidae within the order Cypriniformes. This species is also commonly referred to as the zebrafish, striped danio, or simply zebra fish. The zebra danio has gained tremendous significance beyond the aquarium trade, serving as one of the most important model organisms in scientific research, particularly in developmental biology, genetics, and toxicology studies. The species was first described by Francis Buchanan-Hamilton in 1822, and its scientific name "rerio" is derived from a local Bengali name for the fish.

Physical Description and Size

Zebra danios are small, streamlined fish that typically reach 4-5 centimeters (1.5-2 inches) in length when fully mature, though some individuals may grow slightly larger under optimal conditions. The most distinctive feature of this species is the series of five horizontal blue stripes that run along the length of their silvery-gold body, extending from behind the gills to the base of the caudal fin. These stripes continue onto the anal and caudal fins, creating an unmistakable pattern that gives the species its common name.

The body is torpedo-shaped and laterally compressed, with a small, upturned mouth equipped with a pair of small barbels. Males are generally more slender and slightly smaller than females, with more intense coloration, while females tend to be rounder and fuller, particularly when carrying eggs. The fins are relatively small and transparent with bluish striping, and the species lacks an adipose fin.

Native Habitat and Distribution

Zebra danios are native to South Asia, with their natural range extending across the Ganges and Brahmaputra river basins in northern India, Pakistan, Bangladesh, Nepal, and Myanmar. They inhabit a variety of freshwater environments including rivers, streams, canals, ditches, and ponds, showing remarkable adaptability to different water conditions. In their native habitat, zebra danios are typically found in slow-moving or standing waters with muddy or sandy substrates, often in areas with moderate vegetation.

The natural environment experiences significant seasonal variations in water level, temperature, and flow rate due to monsoon patterns, which has contributed to the species' remarkable hardiness and adaptability. Water temperatures in their native range typically fluctuate between 18-24°C (64-75°F), with seasonal variations, and they naturally occur in both soft and moderately hard water conditions.

Aquarium Requirements and Setup

Zebra danios are among the most adaptable aquarium fish, thriving in a wide range of water conditions, which makes them excellent choices for beginning aquarists. A minimum tank size of 40 liters (10 gallons) is recommended for a small school, though larger tanks are always preferable as these active swimmers require ample swimming space.

The ideal water temperature range is 20-26°C (68-79°F), with a pH between 6.5-7.5, though they can tolerate a broader range from 6.0-8.0. Water hardness should be maintained between 5-19 dGH, and good filtration with moderate water flow is beneficial as it mimics their natural riverine environment. The aquarium should be well-covered as zebra danios are accomplished jumpers, particularly when startled or during feeding time. Substrate choice is not critical, but a darker substrate will help enhance their natural coloration. Live or artificial plants, driftwood, and rocks can be added to provide visual barriers and create a more natural environment, though open swimming areas should be maintained.

Behavior and Social Structure

Zebra danios are highly social, active fish that must be kept in groups of at least six individuals to display natural schooling behavior and reduce stress. In smaller groups or when kept alone, they may become aggressive, stressed, or exhibit abnormal behavior patterns. They are peaceful community fish that occupy primarily the upper to middle water column, constantly swimming in loose schools throughout the aquarium.

Their activity level is consistently high during daylight hours, as they are diurnal fish that rest during darkness. Zebra danios exhibit interesting social hierarchies within their schools, with dominant individuals often leading feeding activities and territorial displays. They are not territorial in the traditional sense but may establish loose pecking orders, particularly during breeding season. The species displays remarkable intelligence and can be trained to respond to various stimuli, which contributes to their value as research animals. Their natural curiosity and boldness make them excellent dither fish for shy species, as their constant activity and lack of fear can encourage more timid tankmates to venture into open areas.

Diet and Feeding

In their natural habitat, zebra danios are omnivorous opportunistic feeders that consume a varied diet including small insects, insect larvae, crustaceans, worms, plant matter, and algae. In aquarium settings, they readily accept most commercial foods and should be provided with a balanced diet consisting of high-quality flake or pellet food as a staple, supplemented with live or frozen foods such as bloodworms, daphnia, brine shrimp, and mosquito larvae.

Their small mouths require appropriately sized food particles, and they are surface feeders that prefer to take food from the upper water column, though they will readily pursue sinking foods. Feed small amounts 2-3 times daily, providing only what can be consumed within 2-3 minutes to maintain water quality. Due to their high activity level and fast metabolism, zebra danios require regular feeding and may lose condition quickly if food is withheld.

Vegetable matter should also be included in their diet through blanched vegetables, algae wafers, or high-quality flakes containing plant matter. Their enthusiasm at feeding time is legendary among aquarists, as they will frantically compete for food in a feeding frenzy that demonstrates their natural competitive feeding behavior.

Breeding and Reproduction

Zebra danios are among the easiest freshwater fish to breed in captivity, being prolific egg-scatterers that can spawn repeatedly throughout the breeding season. Sexual maturity is typically reached at 2-3 months of age or when fish reach approximately 2.5 cm in length. Males can be distinguished from females by their more slender build, brighter coloration, and more pointed fins, while females are fuller-bodied, especially when carrying eggs. Breeding can occur in the main aquarium, but for controlled breeding and fry survival, a separate breeding tank of 40-60 liters with a temperature of 25-26°C is recommended.

The breeding tank should have a shallow water depth of 15-20 cm, fine-leaved plants or spawning mops, and either a layer of marbles or mesh bottom to protect eggs from being eaten by the parents. Conditioning involves feeding high-quality live or frozen foods for 1-2 weeks before spawning. Spawning typically occurs in early morning hours, triggered by gradually increasing light levels. The female can release 200-500 eggs during spawning, which are fertilized externally by the male and fall to the bottom.

Parents should be removed immediately after spawning as they will consume their own eggs. Eggs hatch in 48-72 hours at 25°C, and fry become free-swimming 5-7 days after hatching. Initial feeding should consist of infusoria or commercial fry food, progressing to newly hatched brine shrimp and finely crushed flakes as they grow.

Compatibility and Community Tank Considerations

Zebra danios are excellent community fish that are compatible with a wide variety of peaceful to semi-aggressive species of similar size. Their active nature and schooling behavior make them ideal tankmates for other danio species, tetras, rasboras, corydoras catfish, dwarf gouramis, and many barb species. They should not be housed with very large, predatory fish that might view them as food, nor with very slow-moving or long-finned species that might be stressed by their constant activity or become targets for fin-nipping. While generally peaceful, zebra danios can occasionally nip at long, flowing fins, particularly in smaller tanks or when kept in insufficient numbers. 

Their hardiness and adaptability make them excellent choices for mixed community tanks with varying water parameters, as they can adjust to conditions suitable for their tankmates. Due to their active swimming behavior, they should not be kept with species that require very calm, still water conditions. The species' reputation as an excellent beginner fish is well-deserved, as they are forgiving of water quality fluctuations and beginner mistakes while remaining active and entertaining to observe.

Health and Disease Management

Zebra danios are remarkably hardy fish with strong immune systems, but they can still be affected by common freshwater fish diseases. The most frequently encountered health issues include ich (white spot disease), fin rot, bacterial infections, and parasitic conditions. Their active nature and constant swimming make them excellent indicators of water quality problems, as sick or stressed zebra danios will often display reduced activity levels, loss of appetite, or abnormal swimming patterns. Preventive care includes maintaining excellent water quality through regular water changes, proper filtration, and avoiding overcrowding.

Quarantine procedures should always be followed when introducing new fish to prevent disease transmission. Common signs of illness include clamped fins, loss of color, erratic swimming, gasping at the surface, or visible external symptoms such as white spots, fuzzy growths, or damaged fins. Treatment options vary depending on the specific condition but may include raising water temperature, salt treatments, or medication with appropriate aquarium pharmaceuticals.

The species' use as a laboratory animal has resulted in extensive research into their physiology and disease resistance, making them one of the best-understood aquarium species in terms of health management. Their natural hardiness means that with proper care, zebra danios can live 3-5 years in captivity, with some individuals reaching 7-8 years under optimal conditions.

Special Considerations and Interesting Facts

The zebra danio holds the unique distinction of being the first vertebrate to be successfully cloned and has become one of the most important model organisms in biological research worldwide. Their transparent embryos and rapid development make them invaluable for studying vertebrate development, genetics, and human disease models.

Genetically modified fluorescent varieties, including GloFish, have been developed for both research and commercial aquarium trade, though these modified fish may be restricted or banned in some regions. Zebra danios possess remarkable regenerative abilities, being capable of regenerating damaged fins, scales, and even heart tissue, which has made them subjects of extensive medical research.

They are also known for their consistent daily activity patterns and can be used to study circadian rhythms and the effects of light cycles on behavior. In the aquarium trade, several color varieties have been developed including long-finned, albino, and golden forms, though the classic striped pattern remains most popular. Their jumping ability is exceptional, and secure tank covers are essential as they can leap considerable distances when startled or during feeding excitement.

The species has been introduced to various countries outside its native range and has established wild populations in some regions, though it is generally not considered highly invasive. Their adaptability to cooler temperatures makes them suitable for unheated tanks in temperate climates, and they can tolerate brief temperature drops that would stress many tropical species.

Q: Can I feed my fish only flakes?

A: While flakes can be a staple, it's beneficial to include pellets and freeze-dried foods to ensure a balanced diet.

Q: How often should I feed freeze-dried foods to my fish?

A: Freeze-dried foods should be offered as a supplement, not more than a few times a week, to prevent digestive issues.

Q: Are sinking pellets better than floating ones?

A: It depends on your fish species; sinking pellets are ideal for bottom feeders, while floating pellets suit surface feeders.

How to Handle Overcrowding in Your Aquarium

One of the most common mistakes new tropical fish keepers make is overcrowding their aquarium. It's understandable – with so many beautiful fish species available, it's tempting to add "just one more" to your tank. However, overcrowding can lead to serious health problems for your fish and turn your peaceful underwater paradise into a stressful environment. In this article, I'll explore how to recognize overcrowding, understand its dangers, and learn practical solutions to keep your fish happy and healthy.

What is Overcrowding?

Overcrowding occurs when there are too many fish in an aquarium relative to the tank's size, filtration capacity, and water volume. It's not just about physical space – overcrowding also relates to the biological load (waste production) that your tank's ecosystem can handle.

The "One Inch Per Gallon" Rule for a new aquarium that does not have its biological filtration established.

While this is not perfect, it is a good rule of thumb for most new aquarists.  

Many beginners learn the traditional "one inch of fish per gallon of water" rule. While this provides a basic starting point, it's overly simplified. A single 10-inch fish produces much more waste than ten 1-inch fish, and different species have varying space requirements and activity levels.

A better approach considers:

- Adult fish size (not current size)

- Fish species and their territorial needs

- Swimming patterns (active vs. sedentary fish)

- Waste production levels

- Tank shape and swimming space

Signs Your Aquarium is Overcrowded

Water Quality Issues

- Ammonia and nitrite spikes: Your biological filter can't keep up with waste production

- High nitrate levels: Even with regular water changes

- Cloudy or murky water: Bacterial blooms from excess nutrients

- Foul odors: Indicating poor water quality

Fish Behavior Changes

- Increased aggression: Fish competing for territory and resources

- Gasping at the surface: Insufficient oxygen levels

- Lethargy or stress: Fish hiding more than usual

- Reduced appetite: Stress affecting eating habits

- Fin nipping: Frustration leading to aggressive behavior

Health Problems

- Frequent disease outbreaks: Stressed fish have compromised immune systems

- Slow healing: Minor injuries take longer to recover

- Stunted growth: Fish unable to reach full potential size

- Higher mortality rates: Weak fish succumb to stress-related illnesses

The Dangers of Overcrowding

Poor Water Quality

Overcrowded tanks accumulate waste faster than the biological filter can process it. This leads to:

- Toxic ammonia buildup

- Oxygen depletion

- pH fluctuations

- Increased disease risk

Stress and Aggression

Fish need personal space and territory. Overcrowding causes:

- Chronic stress

- Weakened immune systems

- Territorial disputes

- Bullying of weaker fish

Limited Resources

Too many fish competing for:

- Food (leading to malnutrition in some fish)

- Hiding spots

- Prime swimming areas

- Oxygen

How to Calculate Proper Stocking Levels

Consider Bio-load, Not Just Size

Light bio-load fish: Tetras, rasboras, small barbs

Medium bio-load fish: Angelfish, gouramis, medium cichlids

Heavy bio-load fish: Large cichlids, goldfish, messy eaters like oscars

Factor in Swimming Habits

Active swimmers (like danios) need more horizontal space

Vertical swimmers (like angelfish) need tank height

Bottom dwellers need adequate floor space

Account for Growth

Always research adult sizes and stock based on mature fish dimensions, not the juvenile fish you purchase.  That half inch fry that looks so cute may grow up to 10 - 20 times and turn into an agressive killer in a peaceful tank.  Always know what the general characteritics of the fish species is that you add into your balanced community.

Solutions for Overcrowded Aquariums

Immediate Actions

1. Increase Water Changes

- Temporarily increase water change frequency to 25-30% every 2-3 days

- Monitor water parameters daily

- Use a quality water conditioner

2. Enhance Aeration

- Add an air stone or increase surface agitation

- Ensure proper oxygenation, especially at night

3. Reduce Feeding

- Feed smaller amounts more frequently

- Remove uneaten food quickly

- Consider fasting fish for 24 hours if water quality is poor

Long-term Solutions

1. Rehome Some Fish

- Contact local aquarium stores (many accept healthy fish)

- Reach out to local aquarium clubs

- Ask friends or family if they're interested

- Use online aquarium forums and marketplaces

2. Upgrade Your System

- Larger tank: The best long-term solution

- Better filtration: Upgrade to a more powerful filter system

- Additional equipment: Consider UV sterilizers or protein skimmers

3. Improve Tank Efficiency

- Add live plants to help process waste

- Ensure proper tank maintenance schedule

- Optimize feeding practices

Preventing Future Overcrowding

Plan Before You Buy

The most effective way to prevent overcrowding is through careful planning before making any fish purchases. Take the time to thoroughly research the adult sizes of any fish species you're considering – that cute 2-inch juvenile cichlid might grow to 8 inches within a year. Many beginners make the mistake of stocking based on the small fish they see in the store, only to discover months later that their tank is severely overcrowded with adult fish.

Creating a detailed stocking plan is essential for long-term success. Write down the specific species you want, their adult sizes, territorial requirements, and compatibility with other fish. Calculate the total bioload and ensure it matches your tank's capacity. Once you have this plan, stick to it religiously. It's easy to get tempted by a beautiful fish you didn't originally plan for, but impulse purchases are one of the leading causes of overcrowding. Remember that keeping fish is a long-term commitment, often spanning many years, so make decisions that will work for the entire lifespan of your aquatic pets.

Quarantine New Fish

Establishing a proper quarantine routine for all new fish additions is crucial for maintaining a healthy, uncrowded aquarium. Always quarantine new fish for 2-4 weeks in a separate tank before introducing them to your main aquarium. This practice serves multiple important purposes beyond just preventing disease transmission.

Quarantining new fish prevents you from adding sick or stressed fish to an already delicate ecosystem. A sick fish in an overcrowded tank can quickly spread disease to all inhabitants, potentially causing widespread mortality. The quarantine period also gives you valuable time to ensure your current setup can actually handle the additional bioload. During this time, you can monitor your main tank's water parameters and observe whether your existing fish are showing any signs of stress that might indicate the tank is already at capacity.

Regular Monitoring

Consistent monitoring is your early warning system against overcrowding problems. Test your water parameters weekly using reliable test kits, checking ammonia, nitrite, nitrate, pH, and temperature. Keep a log of these readings to track trends over time. Rising nitrate levels despite regular water changes, or difficulty maintaining stable parameters, often indicate that your tank is approaching or exceeding its capacity.

Daily observation of your fish behavior is equally important and costs nothing but a few minutes of your time. Healthy fish in a properly stocked tank will display natural behaviors, show good appetite, and interact normally with tank mates. Watch for signs of stress, increased aggression, or fish spending more time hiding than usual. Keeping detailed records of your tank's inhabitants, including when each fish was added, their current sizes, and any behavioral changes, helps you make informed decisions about future stocking and quickly identify when intervention might be necessary.

Species-Specific Considerations

Schooling Fish

Fish like tetras and rasboras need groups of 6+ individuals, but in appropriate tank sizes:

- 10-gallon tank: 6-8 small tetras maximum

- 20-gallon tank: 10-12 small schooling fish

Territorial Fish

Cichlids and bettas need ample space:

- One male betta per tank (unless heavily planted with dividers)

- Cichlids need territories; research specific requirements

Bottom Dwellers

Don't forget to count bottom-dwelling fish like corydoras and plecos in your total fish count.

When to Seek Help

Contact experienced aquarists or professionals if you notice:

- Persistent water quality problems despite water changes

- Multiple fish deaths

- Aggressive behavior that won't subside

- Fish showing signs of chronic stress

Creating a Sustainable Environment

Remember, a successful aquarium is about creating a balanced ecosystem, not housing the maximum number of fish possible. A properly stocked tank will:

- Maintain stable water parameters

- House healthy, active fish

- Require reasonable maintenance

- Provide enjoyment for years to come

Handling overcrowding requires prompt action and long-term planning. While it's disappointing to reduce your fish population, your remaining fish will be healthier, more active, and live longer lives in a properly stocked environment. Remember, quality over quantity creates a more beautiful and sustainable aquarium.

The key to successful fishkeeping is patience and restraint. Start with fewer fish than you think you want, establish a stable ecosystem, and only add new fish gradually while monitoring your tank's capacity. Your fish – and your future self – will thank you for taking the time to create an optimal environment rather than an overcrowded one.

By following these guidelines and staying vigilant about your tank's conditions, you'll develop the skills and judgment needed to maintain a healthy, thriving aquarium that brings joy for years to come.

Aquascaping for beginners

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