One of the most fulfilling pastimes is fishkeeping, but there are many myths and false beliefs about it that could endanger your fish or cost you money. These are the most frequent errors and essential information for all aquarists.

1. Myth: Letting a Tank Sit Will Cycle It

Fact: Simply filling a new aquarium with water and letting it sit for weeks does not start the nitrogen cycle. Beneficial bacteria need a constant ammonia source such as fish waste, decomposing food, or pure ammonia, to begin converting ammonia into nitrites and then nitrates.

If you skip this process, you risk “new tank syndrome”, where fish die due to toxic water conditions. Always research fishless cycling or use seeded filter media from an established tank to build up healthy bacteria before adding livestock.

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2. Myth: A Sparkling Clean Tank Means a Healthy Tank

Fact: Over-cleaning especially scrubbing filters or washing media under tap water, removes beneficial bacteria that help keep your tank stable. Without these bacteria, ammonia and nitrites quickly spike, putting your fish at risk.

Instead, clean gently. Rinse filter sponges or bio-media in old tank water, not under the tap, and only clean enough to remove visible debris. Never replace all filter media at once.

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3. Myth: Air Pumps Add Oxygen Like a Cylinder

Fact: Air pumps and bubblers don’t inject oxygen into the water. What they actually do is agitate the surface, which allows more oxygen to dissolve into the tank. Good surface movement from filters or powerheads works just as well.

If your fish are gasping at the surface, it’s usually a sign of poor water quality, not a lack of bubbles.

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4. Myth: No Water Changes With Larger Filters

Fact: Nitrates and other dissolved garbage cannot be eliminated by even the strongest filters. Nitrates can only be efficiently reduced by water changes or tanks with a lot of vegetation. Long-term problems with water quality result from skipping water changes.

Although filters maintain the water's clarity and biological stability, they cannot replace regular upkeep.

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5. Myth: Algae Eaters and Plecos Will Clean Your Tank

Fact: Although algae eaters, plecos, and snails aid in the management of algae and leftover food, tank upkeep is still necessary. Actually, they generate their own excrement and occasionally require more nourishment.

Although they make excellent tankmates, you will still need to manually remove algae, change the water, and vacuum gravel.

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6. Myth: Beginners Find Smaller Tanks Easier

Fact: Although it may appear simpler to maintain a small tank, such as a 20-liter micro aquarium, it is actually more difficult. Because smaller water quantities are less stable, temperature fluctuations, algal blooms, and ammonia surges occur significantly more quickly.

A medium tank (60 to 100 liters) is far more forgiving and offers a steady environment for fish to flourish in for novices.

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7. Myth: Water from an Old Tank Cycles a New Tank Immediately

The majority of beneficial bacteria are found on surfaces, such as filter media, substrate, and decorations, rather than in the actual water. A cycle cannot be established by simply pouring old tank water into a fresh configuration.

Transfer gravel, decorations, or filter media from an established, healthy tank to give it a head start. The bacterial colonies actually reside there.

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8. Myth: Feeder fish are inexpensive and safe to eat

Fact: Poor living conditions and parasites or diseases are common among feeder fish. They can also put predatory fish under stress and contribute to needless bioload.

Feeding prepared diets, frozen foods, or premium live foods like brine shrimp or bloodworms is much safer and healthier.

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9. Myth: Certain Fish Only Consume Fish Feeders

Fact: Almost all predatory fish may be taught to take prepared, frozen, or pelleted meals if they are patient. Feeding live feeders continuously raises the risk of illness and makes it more difficult for your fish to transition later.

A brief period of fasting frequently makes fish more receptive to new diets.

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10. Myth: Fish only reach their tank size

The truth is that fish continue to grow to adapt to their surroundings. Although they may not grow as much on the outside in a small tank, their organs still expand, which can lead to malformations, stress, and shorter lifespans.

Your fish will have longer, healthier lives if you give them the right tank size for their species.

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11. Bonus Myth: The Three-Second Memory of Fish

Fact: Research indicates that goldfish and other fish possess long-term memory, which allows them to recognize their owners, learn when to feed, and even execute basic tricks. They are far smarter than most people think.

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You can keep your fish happy and healthy while saving time, money, and sorrow by avoiding these common aquarium fallacies. Always rely on verified aquarium care facts rather than rumors, whether you're beginning your first tank or honing your aquascaping techniques.

Our goal at Fishut Aqua is to support the success of Australian aquarists. Discover everything you need to create a flourishing underwater world with our selection of aquarium supplies, plants, and maintenance instructions.