Different Substrates for Freshwater Aquariums

What is Gravel Substrate?

• Description: Gravel is often the go-to choice for many aquarists. It’s available in different sizes and colors, allowing you to customize your tank’s look. Keep in mind, there are different materials that gravel can be made from, and some of it affect the way the chemistry of the water works.
• Maintenance: Because of the gaps between the pebbles, gravel can trap debris, so a good cleaning routine is essential. That being said, the gaps can also allow for the waste material to be used for plant food, so there’s a balance.
• Fish Preferences: Gravel suits many fish, like goldfish and livebearers. Some fish like to pick between the gravel, and you don’t want it to be too small that the fish will swallow or choke on the pieces. However, bottom-dwellers like Corydoras or Plecos can prefer softer substrates.
• Cost: Gravel is moderately priced, with costs varying based on size and color.

1. Inert Gravel

• Description: This is generally what people think of when they imagine gravel substrate. It’s substrate that does not break down or affect water quality. It’s rocks.
• Types: Primarily quartz, basalt, and other natural rocks.
• Effects on Water Parameters: Typically inert, meaning they do not alter pH, hardness, or other water chemistry aspects.
• Benefits:
  • Aesthetic variety: Available in various colors and sizes.
  • Safe for most aquarium setups, particularly in community tanks.
  • Easy to clean and maintain.
• Drawbacks:
  • Provides no nutrients for plants, making it less desirable for planted tanks unless supplemented with good root tabs or fertilizers.
  • Some colored gravel can leach dyes over time.
• Good Options:
• Aqua Natural Diamond Black
• CaribSea Eco-Complete
• Natural River Rocks

2. Calcium-Based Gravel

• Types: Usually crushed coral, limestone, and dolomite gravel.
• Effects on Water Parameters: These substrates tend to raise pH and increases water hardness due to the leaching of calcium carbonate into the water column.
• Benefits:
  • Ideal for African cichlids, marine tanks, or any setup requiring hard, alkaline water.
• Drawbacks:
  • Not great for soft-water species or planted tanks that require a lower pH.
  • You need to monitor the water parameters to prevent over-alkalinity, or too high of a pH.
• Good Options:
• Carib Sea Crushed Coral
• Coarse Aragonite

3. Clay Gravel

• Types: Laterite, akadama, and other clay-based substrates.
• Effects on Water Parameters: It can slightly lower pH and hardness due to its ion-exchange properties. So, monitor the water quality if this is something that might affect the tank inhabitants.
• Benefits:
  • Very good for planted aquariums, because it provides a stable environment for root growth.
  • Naturally porous, making lots of space for beneficial bacteria colonize and grow.
• Drawbacks:
  • Can be messy when initially added; thorough RINSING is required.
  • It can be cloudy during water changes if it gets disturbed.
  • These gravels can be more expensive than regular gravel.
• Good Options:
• Seachem Fluorite Red
• Seachem Fluorite Black

What is Sand Substrate?

• Description: Sand gives your aquarium a natural look. It’s available in fine or coarse grains. It can resemble the riverbeds and beaches many fish come from, which is a nice choice for many species.
• Maintenance: Cleaning sand can be a bit tricky. You can use a gravel vacuum, and hold it an inch or two above the sand to such the small debris off the top. It can be time consuming. You also need to stir it regularly to prevent anaerobic zones.
• Fish Preferences: Sand is a favorite among bottom-dwellers like Corydoras, loaches, and gobies. Many fish like to sift and dig in sand, it’s fun to watch! But it’s not ideal for fish that like rocky environments.
• Cost: Sand is generally affordable, but specialty sands might cost more.
• Good Options:
• Aqua Natural Galaxy Sand
• Carib Sea Super Natural Moonlight Sand

What are Dirt/Soil Substrates?

• Description: Organic soil substrates have a ton of nutrients, perfect for planted aquariums. They promote thick plant growth, helping create a thriving underwater garden. Most true aquarium soil is considered Active soil. This soil buffers the waters pH and makes it softer. This is ideal for fish like Rams or shrimp like Caridina’s. Without active soil, the water parameters will fluctuate greatly, which will be harmful to the life of the tank. Inert soil is just regular soil that does not affect water parameters. If you’re looking for soil for your aquarium, or your aquarium plants, be sure to pick the write type of soil.
• Maintenance: These substrates can be messy, usually requiring a sand or gravel cap to prevent the water from clouding. If it does not have a cap, it’s likely for a reason and may not need a ton of maintenance. However, if you’re using active substrate to buffer what quality, this “activeness” will run out after time, and it will need to be replaced.
• Fish Preferences: Ideal for planted tanks with plant-friendly fish. If the soil is not capped, avoid fish that dig, as they may disturb substrate layers.
• Cost: Moderate to high; adding layers of other substrates and plants increases overall expenses.
• Good Options for Active Soil:
• ADA Aqua Soil Amazonia (the best active soil on the market)
• Fluval Plant and Shrimp Stratum

What are Combination Substrates?

• Description: Combining soil with another substrate, like sand or gravel, offers the benefits of the plant feeding soil and looks of the substrate capping the soil. Typically, a nutrient-rich soil layer is topped with sand or gravel.
• Maintenance: Initial setup involves laying the soil layer first, followed by a sand or gravel on top as a cap. Regular cleaning with a gravel vacuum helps manage waste and debris.
• Fish Preferences: Perfect for planted tanks, providing lots of nutrients for plants and a stable surface for fish. Just make sure the layer of capping substrate is thick enough that fish can’t dig to the darted layer.
• Cost: Moderate to high; the price includes soil and top layer substrate, but the benefits make it worthwhile for overall health of the plants.

How to Choose the Right Substrate

Picking the right substrate for your freshwater aquarium means planning ahead and think of your fish’s needs, what plants you want to grow, and your maintenance preferences. As we’ve seen, each substrate type has its own unique benefits and considerations:

• Gravel: Versatile, lots of options, moderately priced; requires regular cleaning to maintain water quality.
• Crushed Coral: Raises pH and suits hard water species; moderate to high cost.
• Sand: Offers a very natural look and is great for bottom-dwellers or sand sifters; moderate cost, but can be a pain to clean.
• Bare Bottom: Easy to clean with no substrate cost, but not suitable for all fish.
• Dirt/Soil: Rich in nutrients for plants; buffers/lowers water pH; moderate to high cost with careful setup needed.
• Combination Substrates: The benefits of soil and top layers’ benefits, moderate to high cost, perfect for planted tanks.

The most important thing to consider when choosing substrate… 1. Does the fish like it? 2. Do you like it? Just have fun, enjoy the process, and take you time.