Seachem Onyx Sand
Also sold as Onyx Sand
Seachem Onyx Sand is a sand. It holds no nutrients of its own and pushes pH up, which is what decides whether it suits your plants and your shrimp.
At a glance
| Type | Sand |
|---|---|
| Nutrients | None (inert) |
| Grain | Fine |
| Brand | Seachem |
| Effect on pH | Raises pH and hardness |
| Ammonia when new | None |
| Shrimp | Suits Neocaridina |
Before it goes in
- Seachem Onyx Sand is a sand.
- It is inert: it holds no nutrients of its own. Root feeders such as Cryptocoryne wendtii and Dwarf Hairgrass Mini need root tabs under them.
- It pushes pH and hardness up. That rules it out for soft-water shrimp and for plants that want acidic water.
- It releases no ammonia, so livestock can go in as soon as the tank is cycled.
- It suits Neocaridina, which want harder water than Caridina do.
What kind of substrate is it?
Sand, fine grain, holding no nutrients of its own.
Does it change pH?
Yes, it pushes pH and hardness up.
Does it leach ammonia?
No, so you are not waiting on it to stop before stocking.
Can I use it on its own?
Yes — Seachem Onyx Sand is a complete substrate on its own.
What it goes with
- Plants that do not care that it is inert, because they feed from the water: Hygrophila corymbosa 'Siamensis', Water Sprite, Anubias nana 'Petite' and Frogbit.
- Animals that are fine on it: Betta, Cherry Shrimp, Goldfish and Angelfish.
Often compared with
| Seachem Onyx Sand | Aragonite Sand | ADA Colorado Sand | |
|---|---|---|---|
| Type | Sand | Sand | Sand |
| Nutrients | None | None | None |
| pH | Raises | Raises | Neutral |
| Grain | Fine | 0.3–1 mm | 1–4 mm |
| Leaches ammonia | No | No | No |
More substrates
Sources (1)
- seachem.comSep 2026