Ryuoh Stone

Also sold as Ryuo · Ryuoh-seki · Ryuoh

Synonyms Ryuoh rock · Ryuo stone

Ryuoh Stone is an aquascaping rock sold by the piece, typically around 16 × 11 × 10 cm (6.3 × 4.3 × 3.9 in). In the water it raises KH and GH, does not tint the water, and sinks straight away.

At a glance

Material	Rock
Raises hardness	KH and GH
Tannins	None
In the water	Sinks right away
Edges	Sharp
Prep	Rinse
Default size	16 × 11 × 10 cm (6.3 × 4.3 × 3.9 in)

Before it goes in

Ryuoh Stone raises KH and GH, so it pushes the water harder and the pH up over time. In a soft-water tank — Chili Rasbora and Green Neon Tetra — use a little of it or leave it out.
Before it goes in, rinse it.
It has sharp edges — worth keeping in mind next to long-finned fish and around fish that sit on the bottom.
4 different pieces of Ryuoh Stone are modelled, so the one you place looks like one you could actually pick out of the bin.
A default piece is 16 × 11 × 10 cm (6.3 × 4.3 × 3.9 in); you can stretch it to whatever you bought.

Does it raise pH and hardness?

Yes — it raises KH and GH, and pH follows. You can check any piece yourself: a drop of vinegar on it fizzes if it is the kind that dissolves.

Do I need to prepare it?

Yes: rinse it before it goes in.

Will it tint the water?

No.

Is it shrimp- and fish-safe?

The water it makes is the thing to check, not the rock itself. It does have sharp edges, which is worth a thought around long-finned and bottom-sitting fish.

What it goes with

Plants you can tie or glue straight onto it: Anubias nana 'Petite', Subwassertang, Anubias barteri and Bucephalandra 'Green Wavy'.
Substrates that pull the other way and soften what it hardens: ADA Amazonia, Akadama and UNS Controsoil.

Often compared with

	Ryuoh Stone	Ancient Pagoda Stone	Black Mountain Stone
Raises	KH and GH	KH and GH	KH and GH
Tannins	None	None	None
In water	Sinks	Sinks	Sinks
Prep	Rinse	Rinse	Rinse

More hardscape

Plan a tank with Ryuoh Stone →

Sources (1)

KHbuceplant.comSep 2026