Sand or fine gravel for the aquarium: which substrate to choose?
Choose sand if your fish sift the bottom (corydoras, loaches, kuhlis) and fine gravel (2-3 mm) for easy maintenance and classic planted tanks. Price-wise, the two are on a par: 1 to 2 € per litre in bags, or 15 to 25 € to cover a 100-litre tank with a 4-to-5 cm layer.
Why does sand change everything for certain species?
Corydoras spend the day sifting the substrate with their barbels: on gravel, they wear down those barbels and injure themselves; on river sand or fine sand (0.1 to 0.8 mm), they express their natural behaviour. It’s genuine enrichment, on the same level as the hiding spots and plants presented in our decor and enrichment category.
What are the concrete advantages of fine gravel?
- Easy siphoning: waste stays on the surface and the gravel vacuum doesn’t swallow it.
- No compacted zones: water circulates between the grains, limiting anaerobic pockets.
- Plant anchoring: roots grip it better than very fine sand.
- Choice of colours: natural quartz, black basalt, light tones — stick to non-calcareous, non-sharp gravels.
Is sand harder to maintain?
A little: you have to siphon by hovering over the surface without plunging the vacuum bell, and stir the open areas every two weeks to prevent compacting. In return, waste stays visible on the surface instead of sinking in. In a low-tech planted tank, a 3 cm layer of sand over a nutrient substrate works very well.
Can you mix sand and gravel in the same tank?
Yes, by zones: a sandy beach at the front for the sifters, planted gravel at the back. Separate the zones with stones or a buried plastic border, otherwise the sand migrates under the gravel within a few weeks. Expect 25 to 35 € for a mixed layout in a 100-litre tank, nutrient substrate not included.
Frequently asked questions
Can beach or builder’s sand be used?
Not beach sand (salt, pollution); quartz builder’s sand such as filtration sand can work if it’s non-calcareous, but rinse it very thoroughly. Test with vinegar: if it fizzes, it’s calcareous — walk away.
How thick should the substrate be?
3 to 4 cm for sand, 4 to 6 cm for gravel with plants. Beyond 6 cm of sand, the risk of anaerobic zones increases.
Should the substrate be rinsed before going in?
Always, in small batches, until the rinse water runs clear: ten minutes of chore that spare you a week of cloudy water.
This guide is part of Planète Pets’s Fishkeeping universe. Our advice is general in nature: for any health concern, your veterinarian remains the only reference.