Aquarium Substrate and Decor: Gravel, Sand, Aqua Soil, Driftwood

Gravel suits most tanks, sand gives a softer look, and aqua soils such as Fluval Stratum are for planted tanks. Driftwood can lower pH through tannins and limestone raises it, says Aqueon, so match decor to your fish. Rinse substrate before use, never use soap, and choose smooth decor for long-finned fish like bettas.

Substrates compared

Aqueon’s setup guide says to rinse gravel with tap water in a colander, wire strainer or fish net, and the Marina kit manual says to rinse gravel and ornaments to remove debris. The Marina manual says to add and spread it carefully, avoiding the walls.

Gravel, sand, aqua soil and hardscape

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Aqua soils for planted tanks

Aqua soils are made for rooted plants. Fluval describes its Plant and Shrimp Stratum as collected from volcanic soil near Mount Aso in Japan, porous so that nitrifying bacteria colonize it quickly, and able to support a neutral to slightly acidic pH. It says to rinse it gently in a colander without stirring, only to remove dust.

If you keep fish-only tanks with artificial plants, plain gravel or sand is enough. Live plants are sold by aquarium retailers; follow their care notes for substrate and light, and see aquarium lighting for PAR.

Driftwood, rock and pH

Hardscape changes water chemistry. Aqueon says tannins from driftwood can lower pH, though one or two small pieces will not do much in a large tank or one with strong buffering. Tannins also tint water the color of tea.

Aqueon also says crushed coral and dolomite gravel, and limestone or coral rock as decor, slowly dissolve, raising and buffering pH. Some fish want that and many do not. Before you add a new rock, ask what it is; aquarium-sold rock is labeled.

Aqueon adds that most captive-bred freshwater fish are flexible about pH, and that changing it is generally not necessary and can do more harm than good. Test with a kit (see how to cycle a fish tank) before and after adding wood or rock, and make changes slowly.

Decor that is safe for fins

For bettas, RSPCA Australia asks for smooth gravel and decor without sharp edges, which can damage fins. University of Illinois vets add that decorations should never take up so much of the tank that the fish is pushed to the edges.

• Silk plants are soft and suit long-finned fish.
• Plastic plants vary; run your fingers over them and skip any with sharp seams.
• Hides and caves give shy fish cover; check the openings for rough edges.
• Backgrounds go on the outside of the back glass and hide cords and walls.

Never use soap or detergent on anything that goes in the tank, says the Marina manual; rinse decor in plain water.

Silk plants, leaf hammocks and backgrounds

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Setting up substrate and decor, in order

The Marina kit manual and Aqueon’s setup guide give the same order, and it saves redoing work:

1. Rinse the substrate in a colander or net until the water runs clearer. Rinse aqua soil gently, as Fluval says, without stirring it.
2. Rinse every ornament in plain water, never soap.
3. Add the substrate carefully, spreading it without scraping the walls.
4. Place rocks, wood and plants on the substrate while the tank is still empty, when heavy pieces are easy to position.
5. Fill slowly with room temperature water, then add water conditioner.

Keeping substrate and decor clean

Waste settles into the substrate between water changes. RSPCA Australia pairs each weekly water change with a gravel clean, which means pushing a gravel vacuum into the gravel so the flow lifts waste out while the stones fall back. Sand is lighter, so hold the vacuum just above it. Decor can be rinsed in old tank water during a change; the cleaning chapter has the full routine.

Putting it together

Choose the substrate for your fish and plants, add hardscape with its pH effect in mind, and leave open water to swim in. The betta setup and goldfish setup chapters give species notes, and the setup checklist covers the rest.