Dragon stone, also sold as Ohko stone, is the holey, eroded rock in warm earthen browns that turns up in a huge number of planted aquariums. It is a clay-based rock and it is water-neutral, so unlike Seiryu stone it will not push your water hardness around.
What dragon stone looks like
Tan to reddish brown, deeply pitted, and full of hollows and crevices that give it the scaled look the name comes from. Those pockets are the reason people reach for it. They hold moss and small epiphytes, they read as caves and overhangs at aquarium scale, and they catch light in a way flat rock does not.
It leaves your water alone
Dragon stone is an argillaceous rock, meaning clay-based, and it does not influence water hardness. It sits with lava rock in the water-neutral group, which makes it the straightforward choice for soft-water scapes and shrimp tanks where stable parameters do more for you than any particular rock shape.
That is the practical difference between the two most popular aquascaping stones. Seiryu contains lime and slowly hardens the water. Dragon stone does not. If you are unsure which you have, the aquascaping rocks guide covers the vinegar test that tells them apart.
Clean it properly first
Dragon stone is notorious for holding loam deposits in its nooks and crannies. Skip the cleaning and the first fill clouds badly, then takes days to clear.
Rinse it hard and brush the pits out before it goes anywhere near the tank. This is the single most common complaint about the stone and it is entirely avoidable.
Planting on it
The texture suits epiphytes, which attach to surfaces rather than rooting in substrate. Anubias, Java fern and Java moss all take to it, and the crevices give you somewhere to wedge a rhizome while it attaches. Just keep the rhizome above the surface rather than buried.
Dragon stone questions
Does dragon stone affect pH or water hardness?
No. It is classed as water-neutral and does not influence hardness, which is what makes it a safe default for soft-water tanks and shrimp.
Do you need to boil or soak dragon stone?
Boiling is not necessary, but thorough cleaning is. Rinse and brush the loam out of the crevices, or the tank will cloud on the first fill.
Dragon stone or Seiryu stone?
Dragon stone if you want a knobbly, cave-like texture and no effect on water chemistry. Seiryu if you want sharp, mountainous grey rock and you are comfortable managing a slow rise in hardness. Use one or the other throughout a scape rather than mixing them.