Aquarium Substrate Guide: Gravel vs Sand vs Soil

The substrate is more than just decoration — it anchors plants, hosts beneficial bacteria, and influences water chemistry. Choosing the right substrate depends on whether you have a fish-only or planted tank, and what species you keep.

Why Is Gravel the Most Popular Substrate?

The most popular substrate. Available in natural and colored varieties. Easy to clean with a gravel vacuum, does not compact, and allows good water flow through it. Best for fish-only tanks and low-tech planted tanks with root tabs. Choose smooth, rounded gravel for bottom-dwelling fish like corydoras.

When Should You Choose Sand as Substrate?

Natural-looking and preferred by many bottom-dwellers. Fine sand can compact and create anaerobic pockets if not maintained. Stir the top layer occasionally to prevent gas buildup. Pool filter sand is an affordable, aquarium-safe option. Best for tanks with corydoras, loaches, and other sand-sifting species.

What Is Aqua Soil and When Should You Use It?

Nutrient-rich soil specifically designed for planted tanks. Brands like ADA Amazonia, Tropica Aquarium Soil, and UNS Controsoil lower pH and provide nutrients for years. The best choice for serious planted tanks. Needs cycling as it initially leaches ammonia. More expensive but worth it for plant growth.

How Deep Should Your Substrate Be?

Aim for 5-7 cm depth for planted tanks (slope from front to back for depth illusion) and 3-5 cm for fish-only tanks. You can layer different substrates — a nutrient base capped with gravel or sand.