Do fish tanks need gravel? Is it absolutely necessary?

By Nadine Oraby | 2020 Update

I still remember the first time I bought a fish tank. I was clueless as to the use of a substrate like gravel. I didn’t know what a substrate was or why should I use it. Well, I found my answer the hard way; let’s make sure you don’t.

To put it simply:

Fish tanks don’t necessarily need gravel to function properly. Gravel is something that is needed to promote a healthy environment for fish to thrive in. Keeping this in mind, while it may not be a necessity, it should be your priority.

Got your answer? Good! Now stick because there is so much for you to learn about substrate in general and gravel in particular.

How to choose substrate for your fish tank (Video)

Gravel is not a necessity, but it should be your priority

Like I have mentioned before, gravel is not a necessity. Your newly bought fish tank will work perfectly without it. But like everything in this life, not every essential thing is a necessity. The same can be said for substrates like gravel.

To understand this, you need to pay attention to what goes on in the fish tank. To put it plainly:

The fish you keep in the tank, eat food, digest it, and produce waste. This process goes on and on until the quantity of waste in the tank reaches a limit that can prove harmful for the fish.

There are two ways to deal with the problem of waste accumulation:

  1. Frequent water changes
  2. Filtration

In case of frequent water changes, you replace the tank water with fresh water. The more the fish, the faster the build-up of waste materials such as nitrates and ammonia, the more frequent the water changes. As you might have already guessed, this becomes a pain.

In the case of filtration, you use a filter to clean the tank water. To do this, you need a separate filter which, as you can guess, costs money. Using a filter doesn’t mean you won’t need to change the water ever again, it just means that the frequency you change the water at, is reduced.

Both of the above cases have their fair share of troubles. This is where gravel makes the most sense. When you use a substrate like gravel, you are helping with waste management.

Baffled? Allow me to explain!

Every habitat on this planet needs a healthy dose of microorganisms like Bacteria to help with waste management. Your fish tank is no different. While it is true that bacteria can grow in a tank with no substrate, the quantity is really low to make any significant difference in reducing waste.

Now, when you use a substrate like gravel, you are essentially giving microorganisms a place to cling on to and grow. Bacterial growth in the case of a substrate is exponentially higher as opposed to the situation in which no substrate is used.

Another reason why you might need gravel has to do with the aesthetic appeal of your fish tank. Pay attention to the natural habitat of fish and will notice that there is a substrate everywhere. Sand, gravel, Corel, to name a few.

In short, using a substrate increases the growth of bacteria, which, in turn, leads to increased waste disposal. This results in fewer water changes.

In addition to reducing water changes, gravel just looks cool, and the fish stand out in such an environment.

What are the different types of substrate and what is best for you?

Substrate comes in many shapes and forms. The type you choose will depend mainly on the type of environment you want to create in the tank.

In general, substrate comes in the following forms:

  • Gravel
  • Sand
  • Corel sand or Corel
  • Marble chippings
  • Marble

Each of these has its advantages and disadvantages, and as such, they all have their particular use cases.

When to choose gravel over sand?

Gravel makes sense in a lot of scenarios. Using gravel as a substrate results in an increased water flow inside the tank. This increased water flow reduces the build-up of harmful microorganisms like the amoeba. In addition to this, the weight of gravel makes it less likely to get sucked into the aquarium filter if you have one installed.

Another reason why you might want to use gravel is its visual appeal. Darker shades of gravel work great as a background against which your fish can stand out.

Seeing this, it is no wonder that gravel is the most widely used form of substrate.

When to choose sand over gravel?

When it comes to fish, some species like to burrow and forage through the ocean floor. If you own such a fish, it is a good idea to get a sand substrate. Sand works exceptionally well in a tank filled with fish who like to burrow.

Another reason why you might prefer sand over gravel is because of its compact nature. Gravel has an abundance of open spaces. Food and other plant-based materials fall through these and settle on the bottom where they rot and decay. This results in an environment that may not be suitable for fish. Sand, on the other hand, doesn’t allow this to happen since there are no open spaces for food and plant wastes to fall through.

Unfortunately, sand isn’t perfect either. Because of its weight, Sand can get sucked into the aquarium filter, where it can cause a blockage. Moreover, I have reviewed some best filters avaialable in the market for your fish tank.

In the end, you should make your final choice after carefully considering the type of fish you own and the type of environment you want to create.

For instance:

If you plan on decorating your fish tank with plants, you need to carefully consider the type of plant you are going to be using and then choose the substrate accordingly. Here are some plants that can grow easily in gravel.

The amount of Gravel needed

The next thing that you need to pay attention to is the amount of gravel you need.

Here’s a simple way to remember it:

You don’t want to overdo it.

For small fish tanks, use up to 3 inches of gravel. For larger ones, increase the quantity by 1 to 2 inches.

Maintenance of the fish tank in case of a gravel substrate

For its faults, gravel is super easy to maintain. It doesn’t get sucked into the filter or dissolve in water, nor does it require frequent changes.

However, a thing needs to be answered here:

Make sure you know when to replace the old gravel for the new one.

To give you an idea, when the substrate becomes slimy and muddy, it’s time to replace it.

Aside from gravel, if you have installed a filter, you must keep an eye on it. It has been seen that filters need to be cleaned more frequently when using a substrate.

Frequently Asked Questions

What color gravel is best for a fish tank?

When purchasing gravel, remember this:

Don’t buy the brightly colored ones.

Bright colors stress out the fish, which can result in a weaker immune system. A weaker immune system equals more chances of getting a disease. So pay attention here.

While we are at it, consider the color and features of your fish. Choose gravel that is muted and yet highlights the best features of your fish.

Can I use crushed coral in a freshwater aquarium?

You can use crushed coral in a freshwater aquarium but only as an add-on and not as a standalone substrate.

Confused? Allow me to explain.

Crushed coral gets dissolved in water and raises its pH. That is to say, it increases the hardness of the water. If you use it as a standalone substrate, it will not raise pH considerably but will also pollute water.

So, to use crushed coral, mix a small amount of it with gravel or any other substrate of your choice.

Is pea gravel safe for aquariums?

Pea gravel is safe for aquariums.

Having said that, keep the following things in mind:

  • Pea gravel has large grains, so it traps more dust and debris than other types of gravel
  • With pea gravel, you’ll need to clean the tank and change the water more often
  • Pea gravel can raise the pH of the water

A good approach is to mix pea gravel with some other substrate and use the mixture.

Can you put rocks in a fish tank?

You can put rocks in a fish tank, but be careful about the type of rocks you use.

Different types of rocks have different qualities. Some rocks make the water hard, some dissolve, and some are inert. Carefully consider your options and then make a decision.

To sum it all up, animals live best when you provide them with an environment that closely resembles their natural habitat. Fish are the same. When choosing a substrate, make sure to choose one that closely mimics the natural habitat of your fish in both function and form. From the nature of the substrate to its form, try to be as precise as possible.

The more time you spend researching and buying, the better your decision will be.

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