Aquarium Substrate Calculator – Find Gravel, Sand & Soil Amount in 5 Seconds

What Is an Aquarium Substrate Calculator?

In 2019, I set up a substrate in a plastic container for lobster roaches to help them grow better. The substrate is the material (like sand, gravel, or soil) placed at the bottom of an aquarium. For fish, substrate is used in the fish tank where it gives them a place to relax, supports good bacteria growth, and holds plant roots in place.

But you might wonder, “How much gravel should I put in my fish tank?” That’s where this online Aquarium Substrate Calculator helps determine the necessary substrate depth, whether you are planning a freshwater, saltwater, or even a reef Tank setup. It helps you figure out exactly how much substrate you need. (Tip: Try to have a wide aquarium volume. An Aquarium Volume Calculator can also help you with this.)

In this simple blog, I’ll share my tips on the best substrate to use, and how to get the right amount. Let’s get started and make your fish tank look amazing!

How to Use an Aquarium Substrate Calculator (Step-by-Step Guide and Expert Tips.

I have a large fish aquarium at my home, ranges 75 to 125 gallons. Suppose you are looking for the best aquarium and don’t know what should be the measurements. You can easily calculate it via this calculator.

✦ Step 1:

Let’s suppose you selected a length of 72 inches like mine aquarium, the width (Depth from from front to back) is 18 inches, and the height is 22 inches. Simply enter your desired value in the above calculator.

• Length: 72 inches (6 feet / 183 cm)

• Width (Depth from front to back): 18 inches (1.5 feet / 46 cm)

• Height: 22 inches (1.8 feet / 56 cm)

• Use inches or centimeters for precise measurements. Most aquarium equipment is labeled in inches.

✦ Step 2:

I recommend a minimum of 2 inches or 5 cm, add this value. Optimal for plants and fish: 3–4 inches (7.5–10 cm). If you have a planted aquarium, then use aquarium soil + gravel. For larger setups, especially those exceeding 55 gallons, the weight of the substrate (measured in pounds or kilograms) becomes a significant factor.

In my native town in Florida, I have native fish like flagfish, Florida gar, and Pugmy, I have added a sand top layer. Don’t use regular garden soil, it can pollute your tank.

Why You Should Care About Substrate (It’s More Important Than You Think!)

✦ What Is Substrate? Understanding Aquarium Substrates.

Substrate is the material (gravel, sand, or aquarium soil) used in aquariums. It depends on the animals or plants you are keeping. Each substrate has its own properties and affects water quality and the ecosystem differently. Always consult an aquarist if you are setting up an aquarium at home.

Also Read: Fish Tank Aquarium Volume Calculator – Find the Exact Fish Tank Size In 4 Seconds

Below, I’ll guide you with tips to help you choose the best aquarium substrate, one that suits your water’s pH and provides best nutrients. I’ve also listed the types of substrates.Understanding them will help you make the right choice for your fish and other marine creatures (like conch sea stars) that people often keep.

✦ Why Substrate Matters for Fish and Plants

• Acts like a home that makes fish feel safe and comfortable
• Gives bottom-dwelling fish places to hide and lay eggs
• Grows good bacteria that clean fish poop from the water
• Catches dirt that you can vacuum up later
• Helps keep water chemistry stable

Substrate Benefits For Plants

It holds plants in place, providing essential nutrients, sometimes supplemented by root tabs, for healthy growth.

• Contains food (nutrients) that plants need to grow
• Turns fish waste into plant food
• Keeps roots healthy by letting water flow through
• Prevents harmful substances from building up

The types of substrate (sand, gravel, or special plant soil) you choose depends on what fish and plants you have. Understanding the different types of aquarium substrate, from fine sand favored by bottom-dwelling fish to coarser gravel or nutrient-rich aquarium soil ideal for planted tanks, is crucial.”

Many aquarists find fi the gravel (2–4 mm) easy to maintain, and easy to clean with a gravel vacuum, which saves time and effort. But some prefer the natural look of sand.

It also provides an excellent surface for beneficial bacteria to grow, like Nitrosomonas, which converts toxic ammonia from fish waste into nitrite, and Nitrobacter and Nitrospira, which then convert nitrite (still harmful) into safer nitrate.

Together, they complete the nitrogen cycle that helps keep your fish safe. Additionally, heterotrophic bacteria break down leftover plant matter into simpler nutrients, preventing sludge buildup in the substrate. Interestingly, these bacteria grow well in fine gravel.

Sometimes, I use sand instead, especially for fish that like to dig or sift through the bottom, such as loaches and corydoras.

Sand offers a more natural feel for many species, keeps waste on the surface for easy cleaning, and creates a soft base that’s gentle on delicate fins and barbels. When properly maintained, sand is compact enough to prevent harmful gas pockets from forming.

If you’re keeping a planted tank, I highly recommend using aquarium soil, especially high-quality options like ADA Aqua Soil Amazonia. It’s rich in nutrients and perfect for growing aquatic plants such as Amazon Sword (Echinodorus) and Dwarf Sagittaria, both of which thrive in nutrient-dense substrates.

Another great option is Seachem Flourite Black, which I’ve also used personally. Several reputable brands, such as CaribSea, and Fluval, offer high-quality aquarium soil. It doesn’t affect your water chemistry and supports healthy fish and plant growth. Choosing the right substrate is key, your aquarium will look better, and your aquatic life will live happier.

Best Substrate Soils for Aquarium Water Chemistry

At the Whitney Lab for Biosciences, we experimented with various aquarium substrates to see how they affect water chemistry. Certain aquarium soil substrates, like ADA Aqua Soil Amazonia and Fluval Stratum, are known to influence the water’s pH, which is an important factor for many tropical fish.

Interestingly, this makes them ideal for tropical fish that come from soft, acidic waters.

We also tested peat moss substrate, a natural material that releases tannins into the water. This gently lowers the pH, softens the water, and gives it a tea-colored tint, similar to natural blackwater environments found in the Amazon and Southeast Asia.

It’s perfect for fish that servive in these conditions, such as tetras, bettas, and other soft-water species.

 Both aquarium soil and peat moss work well for aquariums that need slightly acidic water, and they also support the healthy growth of many popular aquatic plants. On the other hand, crushed coral is a type of substrate that raises the pH level of the water, making it more suitable for hard-water species like African cichlids.

All of these substrates are widely available and easy to use. I’ve personally tried and recommended them, they’re reliable, and you won’t regret using them in your tank. Each one has its own benefits depending on the type of fish and plants you’re keeping.

Substrate for Plant Nutrition

I recommended types of substrates in above paragraph,  they  provide nutrients to your aquarium plants through substrate. First, soil substrates like ADA Aqua Soil Amazonia slowly release nutrients that support strong plant growth in your aquarium. They are especially great for rooted plants.

Second, you can use root tabs. These are nutrient-rich tablets that you insert into inert substrates like gravel or sand. Root tabs deliver essential nutrients directly to the plant roots, making them perfect when you’re not using a nutrient-rich soil.

Calculating Aquarium Substrate Quantity

To calculate the correct amount, you’ll need to consider your tank’s length, width, and desired depth, typically measured in inches or centimeters. Our online aquarium substrate calculator tool can greatly simplify this process.

You can choose the depth of your substrate based on your tank’s purpose. A general guideline is 1 to 4 inches. For planted tanks, a deeper substrate helps promote better root growth. You can also create a slope—higher at the back and lower at the front—which not only looks attractive but also adds depth to your tank’s layout. The right depth and slope give your tank a more natural and visually appealing base.

Aquarium Dimensions and Substrate Volume

To calculate how much substrate you need, first measure the length, width, and height of your aquarium. For example, in a rectangular tank, multiply the length by the width to get the base area. Then multiply that by the desired substrate depth to find the total volume. This will help you estimate how much substrate to buy, usually measured in liters or pounds (or even kilograms, depending on the region

Aquarium Substrate Calculator Usage? Why is it needed?

Our Aquarium Substrate Calculator is not like a regular calculator. It’s easy to use. Just type in your tank size and how deep you want the substrate. It gives you instant ideas and tells you how much you need. It also checks the weight of the substrate and helps you pick the best one for your budget.

One important thing to remember: substrate weight matters. Heavier substrate needs more support. If you choose a thick or heavy layer, cleaning and water changes will take more effort and can affect your tank water. Also, heavy substrate costs more. So always choose the right amount based on your needs and budget.

Setting Up Your Aquarium (Best Tips)

It’s important to choose good-quality substrate and set it up properly. I usually keep the substrate 1 to 3 inches deep. A deeper layer is helpful for plant roots and keeps the water cleaner. For tanks with live plants, I like to use special plant soil (aqua soil) that has nutrients. I also make a gentle slope from front to back. It looks nice and helps stop waste from collecting in the front.

Simple 10 Layering Tips

1. Use about 1.5 inches of substrate for plants with short roots like Anubias, Java Fern, and Moss.
2. Make the back of the tank slope up to around 3 inches to make it look deeper.
3. Wash the substrate before using it to keep the water clear.
4. Start with a bottom layer of plant soil, then add sand or gravel on top.
5. Add more substrate in plant areas where deep roots are needed.
6. Use rocks or dividers to keep the layers in place.
7. You can add a thin layer of laterite or clay underneath for extra nutrients.
8. Put big rocks and decorations in first so they stay stable.
9. When filling the tank with water, pour slowly over a plate or bowl to avoid messing up the substrate.
10. Let everything settle for 24 hours before adding fish or plants.

Aquascaping & Design (Make Your Aquarium Tank Look Nice)

Aquascaping means decorating your tank with plants, rocks, and wood to make it look like a natural underwater scene. It also helps fish feel safe and happy. Creating an appealing aquascape often involves considering the substrate’s color and texture to complement your plants and hardscape.

7 Best Simple Tips

1. Plan First : Think about how you want your tank to look.
2. Put Big Things in the Back : Like tall plants and large rocks.
3. Keep It Natural : Don’t place everything in the middle. Make it look like nature.
4. Leave Space : Make sure fish have room to swim.
5. Use Live Plants: They look good and keep the water clean.
6. Make a Slope : Higher at the back, lower in the front.
7. Choose One Style : Like jungle look or rock style.

Tips for Getting the Right Amount of Sub Strate

✦ How Much Substrate Do I Need?

• 1 inch of gravel: about 1 pound per gallon
• 2 inches: about 2 pounds per gallon

✦ How Deep Should It Be?

• Fish-only tanks: 1 to 2 inches
• Planted tanks: 2 to 3 inches

✦ Pounds Per Gallon Guide

Here’s a quick table:

Tank Size	Substrate Depth	Pounds Needed
10 gal	2 inches	20 lbs
20 gal	2 inches	40 lbs
30 gal	2 inches	60 lbs

(These are just estimates, our calculator will give the best number!)

Going Further: Special Cases for Planted Tanks & Big Aquariums

✦ Planted Aquarium Substrate Calculator Basics

Plants need more depth and nutrient-rich soil. Use our aquarium soil substrate calculator for better accuracy.

✦ What If You Have a 10, 20, or 55-Gallon Tank?

Use the calculator and choose the right depth:

• 10 gal: 10–20 lbs
• 20 gal: 20–40 lbs
• 55 gal: 55–110 lbs

✦ Substrate Layers for Healthy Plants

Some aquarists use layers:

1. Bottom: Soil
2. Middle: Sand or fine gravel
3. Top: Decorative gravel

Frequently Asked Questions

Conclusion

You now have the knowledge and the tool, the aquarium substrate calculator, to confidently determine the precise amount of substrate your aquarium requires. Take control of your aquarium setup, avoid unnecessary waste, and create the ideal environment for your aquatic inhabitants.

Use the calculator today and take the first step towards a more successful and visually appealing aquarium.