Top 9 Freshwater Aquarium Myths & Secrets Revealed

Estimated read time 8 min read

This is a list of some of the most common aquarium myths and secrets that confuse many beginners.

We’ll get into the myth, the truth, and what you should do when setting up a new aquarium.

If you’re sick of reading the old complicated beginner guides then check out our guide: Best Freshwater Aquarium Setup. Check it out!

Let’s go.


1. The Inch Per Gallon Rule

Most beginners think – the more fish you put in an aquarium, the better. And to be honest, an aquarium full of fish, plants, and decor does look awesome!

But is that the right thing to do?

If you’re planning on setting up an aquarium, you may have been told to follow the ‘Inch per Gallon Rule.

While some people may tell you this rule is a must to follow, let us assure you that it’s not, but rather, a very simplified way for a beginner to understand simple stocking guidelines.

According to this rule, you should have only one inch of fish for every gallon of water in your tank. This means, if you own a 10-gallon aquarium, you can have ten inches of fish in total.

For example, you could have the following;

  • Ten fish that are one inch in length each.
  • Five fish that are two inches in length each.
  • Three fish that are three inches in length each.

However, not all fish grow to be the same size and shape, nor do they produce waste in equal quantities. Moreover, a 10-gallon fish tank won’t even hold 10 gallons once you factor in the substrate, rocks, plants, filters, and of course, fish!

While this rule gives a rough idea of how many fish you should keep in your tank, it is not the best way to determine how many fish you can keep in your tank.

2. Tropical Fish Will Only Grow To The Size Of The Aquarium

Another common aquarium myth is that fish only grow as big as the aquarium they are kept in. If you think your fish will grow big in a large aquarium, we’re sorry to break it to you, but that’s not how it goes.

Unfortunately, fish don’t grow as big as the aquarium they are living in.

It’s not the size of the aquarium that affects the fish’s growth, but the species and the conditions of the fish tank. Is your water clean and clear, or is it dirty and toxic?

All these things will impact the health of your fish.

If your fish doesn’t seem to grow to its full size, it may have health issues that were caused by poor water quality or just might have stunted growth or deformed.

In some cases, improving your tank conditions can have a positive effect on fish’s growth, but more often than not, there may be long-term, lasting effects.

So, if you think changing the size of the fish tank will help your fish grow larger, trust us – it won’t!

3. Small Tanks Are Better For Beginners

If people keep telling you that you should start with a small aquarium, don’t believe them.

You’ll be surprised to know that a small aquarium is much harder to maintain. The mortality rate of fish in a small fish tank is also quite low.

Fish need to have room to swim, prefer a tank that reflects their natural environment like any other animal.

Keeping your fish in a small aquarium, especially Goldfish, is a bad idea. Your fish won’t have enough room to swim around, they won’t be comfortable, and the quality of water is hard to maintain.

So you get a bigger tank.

4. You Can Add Fish Right Away

No, you can’t put fish in your tank right away.

Adding fish to your aquarium too soon can be dangerous for them. New fish tanks require some time to get to develop beneficial bacteria, which ultimately creates healthy water conditions for your fish.

There are many gasses, heavy metals, minerals, and chemicals added to the water system that can harm the fish in your aquarium.

By waiting, you allow the water time for gases to escape, pH, and harmful materials become neutralized. The filtration system circulates the water and starts to develop healthy bacteria colonies.

Be patient, and let your aquarium work through the nitrogen cycle before adding fish to it.

5. What To Do And Not Do When Cycling Your New Tank

Cycling your new fish tank is essential to ensure the wellbeing of your fish. The water from your tap is often high in chemicals, nutrients, and minerals.

Cycling the fish tank is a process of developing nitrifying bacteria that kick off the nitrogen cycle, which is how the toxic nitrogen compounds like ammonia are converted into nitrates.

You may not be aware of it, but ammonia can cause serious harm to the health of your fish. The ammonia in the water needs to be entirely removed before introducing fish to it, and that’s what cycling a tank means.

The first thing you should do when cycling your new tank is to let the tank sit. Let it stand for a day or two and allow beneficial bacteria to grow; it needs this to initiate the cycle.

After you’ve let your aquarium stand, check the water parameters and add fish to your tank only if the ammonia and nitrite levels are zero.

Further Information: How to cycle your aquarium. For step by step instructions.

6. An Aquarium Needs A High Ammonia Level To Cycle

Have you ever heard that aquariums need a high level of ammonia to cycle?

Well, widespread as this misconception is, it holds no truth.

Any amount of ammonia can help your tank cycle. As long as you have ammonia present, the tank can cycle. That said, the more ammonia present in your tank can impact how fast your tank cycles.

However, high levels of ammonia can kill your fish. The primary reason for cycling is to bring ammonia levels down to zero! Cycling is a process of nourishing beneficial bacteria to convert harmful ammonia into less harmful nitrates.

In the beginning, since there are not enough bacteria to convert all the ammonia into nitrates efficiently, higher quantities of ammonia will be present in the water column.

And that’s the only time high ammonia levels are okay.

7. Don’t Do Water Changes While Your Aquarium Is Cycling.

If you’ve discussed setting up an aquarium at home, you may have been told not to change the water while your aquarium is cycling.

It’s believed that performing water changes when aquariums are cycling disturbs the cycling and impacts bacteria growth.

However, the truth is that it can be beneficial to complete small water changes to help dilute nitrites and ammonia—especially when using fish-in cycling methods.

Another common misconception is that a water change reduces the number of bacteria in the tank. However, bacteria grow on all surfaces inside the aquarium like the rocks, gravel, and glass.

So, even if you do remove some water, the bacteria won’t be removed along with it.

8. You Need An Air Pump And Air Stones For Oxygen

One of the biggest misconceptions when it comes to setting up aquariums is that you need an air pump and air stones for the oxygenation of the water.

The air pump doesn’t directly provide oxygen to your fish. An air pump improves the circulation inside your tank and increases the surface area agitation. That is it!

This circulation and added surface agitation is a good benefit; however, it isn’t required, and your fish can do very well without an air pump and air stones.

So, no – you don’t need an air pump and air stones for oxygen.

9. You Can’t Overstock A Tank.

How many times have you been told that you can’t overstock a tank?

Overstocking is a thing.

To put it simply, when you overstock a tank, the amount of fish waste being produced overwhelms the beneficial bacteria, and they can’t keep up.

This causes high ammonia and nitrite levels, algae blooms, toxic water condition, and ultimately fish will die.

The fish also won’t have enough room to swim; they will become stressed, territorial start to fight and injure each other.

If you don’t want to impact the quality of life of your fish, don’t overstock your tank!

Closing Word On Myths

Before you set up your aquarium, make sure you know what’s a myth and what’s the truth.

The fact is maintaining aquariums full of healthy fish might not be easy for a beginner, but once you get hold of the basic dos and don’ts, you’re all set to pull off your hobby like a pro and keep your pet happy and healthy.

Thanks for reading!

This article is part of a large series of articles to help you understand the benefits, myths, cost, and steps you need to take to set up a successful aquarium.

Below are links to the next and previous chapters in this series.

Now let’s get started on setting up your new aquarium.


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