Dragon Stone, also called Ohko stone, has warm brown-red tones, deep grooves and a relatively brittle clay-like structure. Reputable aquarium suppliers describe it as inert. Seiryu Stone is grey-blue with white veining and sharper mountain-style texture, but it can gradually raise water hardness and pH. Both should be rinsed thoroughly and arranged securely before the tank is filled.
The visual difference is obvious; the chemistry difference is the one that matters most when choosing between them.
Dragon Stone characteristics
- Earthy brown, yellow and red tones.
- Deep holes and weathered texture.
- Relatively brittle and easy to shape.
- Generally sold as inert and not expected to change water parameters.
Seiryu Stone characteristics
- Grey to blue-grey colour with pale veining.
- Sharp craggy texture suited to Iwagumi and mountain layouts.
- Dense and structurally strong.
- May gradually increase pH and water hardness.
Chemistry should influence the choice
If you are deliberately maintaining soft, low-KH water, Dragon Stone is the simpler option. In a hard-water tank, Seiryu's mineral effect may be less problematic or even compatible with the livestock.
Test GH, KH and pH rather than assuming an active soil will completely cancel the stone's effect.
Both need preparation
Dragon Stone often contains clay and dust in its crevices, while Seiryu can also arrive dusty. Rinse and brush both thoroughly before use.
Do not use soap or household cleaners.
Build stable hardscape
Set heavy stones securely before adding livestock. Avoid pressure points directly against unsupported glass and make sure digging fish cannot undermine the main structure.
Related aquarium tools and guides
Frequently asked questions
Does Dragon Stone raise pH?
Aquarium suppliers generally describe Dragon Stone as inert, so it should have little effect on water chemistry.
Does Seiryu Stone raise pH?
It can slightly raise pH and water hardness because of its mineral composition.
Which stone is better for Iwagumi?
Seiryu's strong ridges and grey mountain-like appearance make it especially popular for Iwagumi, though other stones can also be used.
Sources and further reading
This guide separates general aquarium arithmetic from fish-welfare decisions. For species-specific limits, always check the needs of the fish you intend to keep.