Why should I use aquarium gravel in my tank?

Last Updated on July 1, 2021 by cmoarz

Aquarium gravel is fun! It comes packed in a variety of shapes, colors, sizes, and qualities. And let’s not forget that nostalgic smell (That, with a combination of various species’ poop, is what makes that famous pet store smell!). Poop aside, Aquarium gravel has many important functions and isn’t meant to just look pretty.

reasons to use aquarium gravel in your fish tank

Filtering and capturing biological contamination.

Filtering waste is one of the most important things aquarium gravel does. The gravel also gives friendly bacteria a place to call home so they can continue doing what it is that they do best. This is important for an aquarium habitat.

Believe it or not, fish aren’t clean creatures. And they really don’t need to be, as they have an entire ocean to crap in, at least they should. Fast forward to that tiny tank on your desk, even with that nice expensive filter you happen to be using, it’s really not going to be enough.

The act of capturing waste and having beneficial micro-organisms living in the rock is kind of a double hitter. The good bacteria use that waste as a source of energy by breaking down all the poop, uneaten food, and other biological garbage that tends to build up in the fish tank otherwise.

This is a vital action and without these bacteria, the water would quickly become inhospitable to your fishy friends in the form of very high ammonia and nitrite levels. In turn, this requires you to increase the frequency you must change the water, which by itself might not even be enough.

Remember those bacteria we talked about? Sure they can exist without aquarium gravel, But the problem lies in how much they can reproduce without it. Obviously, the bigger colony you have, the better off your tank health is going to be. Gravel provides that perfect breeding ground, nursery and all.

What are ammonia and nitrates exactly?

the chemical sequence of ammonia-nitrate
This is supposed to be what ammonia-nitrate looks like. SCIENCE BITCHES

This is supposed to be what ammonia-nitrate looks like. SCIENCE BITCHES

Nitrates are an odorless clear (colorless) gas bi-product from ammonia, which is a common thing to have in an aquarium. When old food, fish poop, and plants decompose, they release ammonia-nitrate, hence the name. Ammonia is extremely toxic to your little fish friends in high concentrations.

Specially designed bio-filters are used in aquariums in order to filter out and break down ammonia into its bi-products (nitrates) which fish can more easily tolerate. But too high nitrate levels are also toxic to your habitat.

To get into a bit more detail on what causes ammonia buildup, you have to factor in just the sheer volume of waste an aquarium can actually produce. This is especially true when you try to pack too many critters into a tank that just isn’t big enough or has an adequate enough filter to treat the water.

Overcrowding also tends to lead to another big ammonia producer – Overfeeding. The more waste food that sits on the bottom, the harder your micro-bacteria has to clean it all up. Add all fatty McOverFedFishFace’s poop into the mix and you can easily overload your environment’s natural ability to break down ammonia.

Obviously, that isn’t ideal.

WHAT? But your fish died after only a year? Oh, what gives! Yeah, that’s correct, It was because of ammonia and nitrate buildup.

Are there alternatives to dealing with nitrites and ammonia levels aside from just gravel?

There are several things you can do in combination to adding gravel to your aquarium.

  • Clean your gravel with an aquarium vacuum

  • Change the water in your tank in order to dilute it

  • Feed your fish less food if they aren’t eating it all

  • Get a bottom feeder to go along with your tank

  • Remove dead biological matter (plant, fish etc)

  • Make sure you are using a filter rated to remove ammonia and nitrates (biological filter)

  • Be sure the size of the tank matches the needs of your fish, is it too small?

  • Chemicals

These things should help deal with ammonia levels if you are having problems, but only in combination with gravel (or a substrate). You have very little chance to keep up with high ammonia and nitrate levels if you have a bare tank.

Aquarium gravel looks really cool

an example of nice aquarium using aquarium gravel
Please don’t use spongebob decorations their so tacky

Just because you can’t directly see all the beneficial things aquarium gravel is doing for your tank, aside from clearer water that is, doesn’t mean it’s not pretty! Like I said in the opening paragraph of this article, aquarium gravel comes in a huge variety of shapes colors, and sizes.

You can do a lot of really cool thing’s with it too when designing a neat habitat. Like the example image above, Imagine trying this tank without all that vibrantly colored gravel? Add a few LED’s and you’ve got an amazing setup! (Please read our article on setting up LED’s in your tank safely before trying this at home.!)

How much gravel should I use in my tank?

To begin with we need to understand that your aquarium should have the right type and right quantity of gravel or substrate. The layer that makes up the substrate could be a combination of sand, aquarium gravel, and rocks.

In most cases, sand makes up the major portion of the substrate with a layer of gravel over top. Getting the specific right answer for you depends on various factors. Let us share the main factors that could give the right answers to the above questions.

Main Factors To Consider

The Type of Fish & Number of Fishes

Too many fish in a crowded tank

We all know one of the main reasons someone would have an aquarium is to keep fish. Hence, the quantity of gravel that you need is directly proportional to the types of fish that you have in the aquarium.

The number of fishes that you plan to have should also be taken into account before you fill the aquarium with the right quantity of gravel. We need to understand that some types of fish are comfortable with coarse gravel. They like to mess around in it. On the other hand, there are other fishes that prefer gravel that is finer.

This is because these fishes are happy foraging and digging around the gravels. Therefore, you may need to understand the behavior pattern of the fishes before you actually decide on the types of gravel and the quantity that you may need.

Aquarium plants and gravel

The Plants

You should also have a clear idea about the plants that you wish to have in the aquarium. For example, when you have plants without any root system, they don’t care much about the type of gravel and the amount of gravel.

This is because these plants get all their nutrients from the water. But if you plan to have rooted plants, then you must be more careful and make sure that the gravel amount is sufficient enough to support the plants and also the fishes that make use of it.

Big rooted plants will need gravel that is fine. Further, the layer should also be deeper. These types of plants will most certainly be top-heavy and therefore they need a generous quantity of nutrients. These trees will not be able to survive and grow properly unless they are able to establish their roots firmly.

So, for the plants with roots, you must have a compact and thick layer of gravel. On the other hand, smaller plants that survive on water-based nutrients require very little gravel. That is why many people prefer going in for plants that do not have roots.

Decorations & Size

The size of the aquarium is also another important determining factor when it comes to answering the question of how much gravel for an aquarium. The same also applies to the decorations that you plan to have for your aquarium.

If you want your aquarium to have large-sized decorations, you must ensure that the amount of gravel is also complementary to it. Otherwise, the aquarium may look bland and listless. You should also do some research and look for some colored gravels and this will add beauty and sophistication to your aquarium.

Just remember to keep the type of gravel or substrate that you buy compatible with the fish or other critters that are living in the tank.

Some Rough Calculations About The Amount of Gravel Required

Once you have considered the above into account, your task of choosing the right gravel should not be much of a problem. The rule of thumb is to start with around 2 inches of gravel for any type of freshwater aquarium. This is also considered the minimum and even the simplest of aquariums should not go below this threshold, as far as gravel and substrates are concerned.

A tank of around 55 gallons having a measurement of around 49 inches by 12 inches would require roughly around 30 pounds of gravel for a bed that is around one inch. Once this has been worked out, the rest becomes easy. You have to just multiply the depth making use of inches. To put it simply, for a two-inch bed you would require 60 pounds of gravel.


Owner of AquariumGravel.com and also owner of actual Aquarium Gravel believe it or not! ;). Setting up beautiful aquarium sceneries and habitats since I was very young. Enjoy!

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