How much substrate do I need per gallon?

When setting up a new aquarium, one of the most important decisions you’ll make is choosing the right aquarium substrate. Aquarium substrate refers to the material that covers the bottom of the tank, providing a surface for beneficial bacteria to colonize and for plants to root in. The substrate also affects water quality and chemistry, so getting the right amount is crucial for the health of your tank.

Quick Answers

Here are some quick answers to common questions about aquarium substrate:

  • 1-2 pounds per gallon is a good general rule of thumb for substrate depth in most aquariums.
  • Deeper substrates around 2-3 inches are recommended for heavily planted tanks.
  • Thinner substrates around 1 inch can work for tanks with just a few plants.
  • Fine gravel substrates take 1-1.5 pounds per gallon.
  • Coarser sands and gravels take closer to 2 pounds per gallon.
  • Soil-based planted aquarium substrates are usually around 1.5-2 pounds per gallon.
  • Always rinse gravel thoroughly before use to remove dust and debris.
  • Slope substrate towards the back for a more natural look.
  • Add substrate supports to prevent slope collapse over time.

Substrate Depth Recommendations

When deciding how much aquarium substrate to use, the first consideration is how deep you want the substrate layer. Here are some general guidelines for substrate depth in different setups:

  • Planted tanks: 2-3 inches deep. Deeper substrate gives plant roots more room to spread out and anchor themselves. Aim for 2-3 pounds of substrate per gallon.
  • Tanks with driftwood/rocks: 1-2 inches deep. You want some substrate to sink pieces in, but don’t need a deep layer. 1-1.5 pounds per gallon is sufficient.
  • Barebottom/lightly planted tanks: 1 inch or less. Barebottom tanks have no substrate at all. Tanks with just a few plants need less than 1 pound per gallon.
  • Standard community tanks: 1-2 inches. This provides some planting space without wasting substrate. Use 1-2 pounds per gallon.

No matter what type of tank you have, resist the urge to use a thicker substrate than needed. Excessive amounts are wasteful and can cause problems with anaerobic pockets.

Substrate Types and Amounts

The exact amount of aquarium substrate needed per gallon depends partially on the type of substrate used. Here’s how to choose the right amounts for different options:

Fine Gravel

Fine gravels include substrates with grain sizes from 1-3mm. Common examples are plain aquarium gravel and Estes Marine Sand. These fine substrates require less material to hit a given depth.

For fine gravels, use:

  • 1 pound per gallon to create a 1 inch layer
  • 1.5 pounds per gallon to create a 2 inch layer

Medium/Coarse Gravel

Medium to coarse gravels have grain sizes ranging from 3mm up to around 1 cm. Substrates like large river rock and some decorative gravels fall into this category. The larger grains take up more volume.

For medium/coarse gravels, use:

  • 1.5 pounds per gallon for a 1 inch layer
  • 2 pounds per gallon for a 2 inch layer


Sands have very small grain sizes under 1mm. Pool filter sands and specialty aquarium sands work well. Like fine gravels, sands take less material for a given depth.

For sand substrates, use:

  • 1 pound per gallon for a 1 inch layer
  • 1.5 pounds per gallon for a 2 inch layer


Soil substrates are less dense than mineral options. Products like Fluval Plant and Shrimp Stratum fall into this category.

For soil/dirt substrates, use:

  • 1.5 pounds per gallon for a 1 inch layer
  • 2 pounds per gallon for a 2 inch layer

Other Substrate Tips

Here are a few other things to keep in mind when adding substrate:

  • Rinse well: Always rinse gravel, sand, or other loose substrates before adding them. This prevents cloudy water from dust and debris.
  • Slope substrate: Creating a sloped substrate that’s higher in the back helps achieve a natural look. Support may be needed to prevent collapsing.
  • Use supports: Plastic mesh and other supports can help stabilize sloped or deep substrates. This prevents compression and settling over time.
  • Add slowly: Place substrate slowly and gently to avoid scratching the tank bottom or clouding the water.
  • Top off: After filling, let the tank settle then top off the substrate if any depressions appear.

Planted Tank Substrate Guide

Heavily planted aquariums often use specialized planted tank substrates designed to provide nutrients and support plant growth. Here’s what you need to know about choosing the right planted tank substrate and amount:

Types of Planted Tank Substrates

Some common types of aquatic plant substrates include:

  • Soil/dirt: Contains organic matter to release CO2. Can create messy water without care.
  • Sand/gravel: Inert substrates that require added fertilizer. Easy to clean.
  • Enriched gravels: Contain integrated fertilizer for plant growth. Require less added nutrients.
  • Clay/clay mix: Denser substrates that bind nutrients for plant roots. Help stabilize pH.

How Much Planted Substrate Per Gallon?

For planted aquarium substrates, use:

  • 1.5-2 pounds per gallon for a 2 inch layer
  • 2-3 pounds per gallon for a 3 inch layer

Aim for substrate depths of at least 2-3 inches in planted tanks to give plant roots space to spread out. This generally equates to 1.5-3 pounds of substrate per gallon.

Nutrient-Rich vs. Nutrient-Poor Substrates

Plant substrates fall into two categories:

  • Nutrient-rich: Contain fertilizers and organic matter. Help plants establish but can eventually deplete.
  • Nutrient-poor: Lack fertilizers, requiring you to dose the water column. Don’t become depleted over time.

If choosing a nutrient-rich substrate, you’ll need a smaller amount of material since nutrients are built-in. For nutrient-poor options, use more substrate to allow plant roots to spread out and search a larger area for nutrients.

Setting Up Substrate in a New Aquarium

Here is a step-by-step guide for adding substrate when initially setting up an aquarium:

  1. Wash the substrate thoroughly and let soak to remove dust.
  2. Add a filtration-friendly base layer like peat or mesh if desired.
  3. Slope the substrate higher in the back with supports as needed.
  4. Plant foreground plants first, then fill in the middle and background.
  5. Add any hardscape materials like driftwood or rocks.
  6. Top off low spots after the tank settles, then fill slowly to avoid disturbing plants.
  7. Allow the tank to cycle before adding livestock.
  8. Perform regular water changes and maintenance to keep the substrate clean.

Taking the time to properly prepare and install aquarium substrate helps create a healthy, aesthetically-pleasing environment for fish and plants to thrive.


Why does substrate depth matter?

Deeper substrate beds provide more room for plant root systems to spread out and anchor themselves. For heavily planted tanks, aim for 2-3 inches of substrate. Fish-only tanks only need thinner layers around 1 inch.

Is gravel or sand better for aquarium substrate?

It depends on the tank inhabitants! Sand allows plants to root easily and won’t harm sensitive fish. Gravel provides more space for debris to settle below the grains, making cleanup easier. Personal preference also plays a role.

How much substrate do I need for a 10 gallon tank?

For a standard 10 gallon aquarium, you will need approximately 10-20 pounds of substrate, depending on the desired depth. 1 inch of substrate takes about 10 pounds. 2 inches requires closer to 20 pounds.

Do I need to replace aquarium substrate periodically?

In most cases you can keep using the same substrate indefinitely as long as you perform regular maintenance like gravel vacuuming and water changes. Substrate replacements every 2-4 years can be beneficial for heavily stocked tanks.

Can I mix different substrate types together?

It’s possible but not always advised. Similar grain sizes work best, as fine substrates on top will just sift down between larger grains. Contrasting colors can look nice blended though. Go slowly and test different combinations.


Choosing and properly installing the right amount of substrate establishes a solid foundation for any aquarium’s ecosystem. While general guidelines exist for how much is needed per gallon based on the type used, also consider factors like the tank inhabitants, plants and hardscape when deciding on substrate depth and quantity. An ideal substrate bed offers ample room for plant rooting, beneficial bacterial colonization, and natural aesthetics.

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