Choosing your first aquarium substrate feels a bit like choosing the flooring for your house: carpet, laminate, or wood? Anything can be beautiful, but some choices are more convenient, practical, and better for your inhabitants. When I set up my first tank, I just thought, "Looks nice." But then again... my Corydoras were sitting on sharp gravel with sore bellies, and my plants looked like they were on a crash diet. 😅 Since then, I've known: the substrate is the foundation, literally and figuratively.
Choose soil for plant tanks (nutrient-rich, at least 4 cm thick). For fish tanks: sand (0.5–2 mm) or rounded gravel (2–5 mm or larger). Corydoras prefer soft, rounded sand; soil often makes the water softer and slightly more acidic.
What is the difference between soil, sand and gravel?
Gravel – Consists of rounded pebbles of approximately 2–5 mm. Easy to clean and ideal for fish tanks without many plants. Note: Avoid sharp gravel for bottom-dwelling fish. Gravel is inert and won't alter your water parameters.
Sand – Fine and soft material, 0.5–2 mm, perfect for fish that like to burrow, such as Corydoras or loaches. It's taut, looks natural, and prevents injury. Fine sand can build up, so loosening it occasionally prevents oxygen-poor areas.
Soil – A favorite among plant enthusiasts: small granules of clay or baked material packed with nutrients. Ideal for rooted plants like Cryptocoryne and Echinodorus . Soil often lowers the pH and softens the water—good for plants, but not always for hardwater fish. Some ammonia may be released during the initial setup; test your water regularly.
Which substrate is best for my aquarium?
- Determine your goal: Do you want a lush planter? Choose soil. Are you focusing on fish and ease of maintenance? Choose sand or gravel.
- Check your inhabitants: Corydoras and loaches prefer soft sand; large cichlids prefer coarser gravel; shrimp thrive in soil or fine gravel.
- Pay attention to your water parameters: Soil makes water softer and more acidic (pH 6–6.8). Gravel and sand keep the values stable and neutral (pH around 7–7.5).
- Maintenance: Vacuum the gravel, loosen the sand occasionally, leave the soil alone as much as possible.
- Mix & match: Combine soil at the bottom with a thin layer of sand or gravel on top — beautiful and functional for plants and fish.
What are common mistakes with aquarium substrates?
- Using sharp gravel: Bottom fish can injure themselves on it — always choose rounded gravel.
- Too thin a soil layer: At least 4 cm is required for healthy root growth (5–8 cm for larger plants).
- Allowing the sand to become too compact: Stir it occasionally or add snails and Corydoras to turn it over.
- Planting in pure gravel without nutrients: Use root tabs or liquid food for sufficient nutrients.
How do I maintain the bottom of my aquarium?
Your substrate thrives in your tank. With sand, use a card or fork occasionally to keep it aerated. Soil? Don't vacuum it, just siphon off the water above it. You can vacuum gravel. Remove any visible debris or leftover food, as these can cause algae or harmful bacteria. Healthy substrate smells neutral, not musty.
Checklist: What you shouldn't forget
- Choose soil based on your residents and purpose.
- Soil for plants, sand for bottom-dwelling fish, gravel for general fish tanks.
- At least 4 cm soil layer for good root growth.
- Rounded granules = safe for fish.
- Use root tabs with sand or gravel.
Conclusion: which substrate is suitable for your aquarium?
The substrate is literally the foundation of your aquarium. Soil for a lush plant garden, sand for active bottom-dwelling fish, and gravel for a low-maintenance fish tank. This way, you build a healthy, stable base and give your inhabitants the best underwater habitat. 🌿🐠
👉View our substrate range for gravel, sand and soils.
👉 Discover plant food and root tabs for extra growth power.
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