Batu Akuarium: Seiryu, Dragon Stone & Are River Rocks Safe?

Batu akuarium (aquarium rocks) do more than decorate. Some are inert and change nothing, while others, like seiryu stone, slowly raise pH and hardness. Before you buy or collect any rock, ask two questions: does it change my water, and is it clean and sharp-free? Seiryu and other limestone-type rocks suit livebearers and African cichlids but not soft-water shrimp. Dragon stone, lava rock and most granite are safe for almost any tank. River rocks can be used too, if they pass the vinegar test and are collected legally. Here is how to choose.

Common Aquarium Rocks Compared

Rock	Look	Effect on water	Best for	Watch out for
Seiryu stone	Grey-blue with white veins, sharp ridges	Raises pH and KH/GH (contains calcium carbonate)	Iwagumi scapes, livebearers, goldfish	Not ideal for Caridina shrimp or soft-water biotopes
Dragon stone (ohko)	Brown-orange, holey clay rock	Inert	Nature scapes, shrimp tanks	Crumbly; holes trap dirt, scrub well
Lava rock	Black or red, very porous	Inert	Plant attachment, bacteria surface, filters	Sharp edges can scratch fish
Slate	Flat grey sheets	Inert	Caves, terraces, cichlid spawning sites	Check for metallic streaks
Granite / river pebbles	Smooth, rounded	Usually inert	Riverbed scapes, loaches, goldfish	Test anything collected
Limestone / coral rock	White or cream	Strongly raises pH and hardness	African cichlid tanks, marine	Avoid in planted and soft-water tanks
Petrified wood	Wood-patterned stone	Mostly inert	Nature scapes	Can be heavy and expensive

Browse options on FishyHub's driftwood, rocks and stones page.

Why pH Matters with Malaysian Tap Water

Much of Malaysia's tap water is soft with low KH. That makes it easy for rocks to push your water around. A big pile of seiryu in a soft-water tank can raise KH and pH noticeably over weeks. That's good news for guppies, mollies and platies, which like harder water, and bad news for crystal red shrimp, wild bettas and blackwater setups. Test pH and KH before and after adding a lot of rock. Our tap water guide explains soft water in more detail.

Seiryu without the pH rise

If you love the seiryu look in a shrimp or soft-water tank, use less of it, combine it with aqua soil (which buffers pH down), and do regular water changes. Some keepers also choose look-alikes that are inert.

The Vinegar Test (Ujian Cuka)

Use this to check any rock, especially ones you collect yourself:

1. Clean and dry the rock.
2. Drip a few drops of plain white vinegar (cuka) on it, or soak a chip of it in a cup of vinegar.
3. Fizzing or bubbles means the rock contains carbonate (limestone, marble, shells) and will raise pH and hardness.
4. No reaction means it's probably inert. Test several spots, because veins can differ.

The test is a quick guide, not a laboratory analysis. If you rely on very stable soft water, also test pH and KH after the rock sits in a bucket of water for a week.

Are River Rocks Safe? (Batu Sungai Akuarium)

Many Malaysian keepers ask if they can use batu sungai from a stream or beach. They can, with care.

Safety

• Avoid rocks with rusty streaks, metallic shine or strong colours, which may contain metals.
• Avoid rocks from drains, industrial areas, construction sites or near farms that spray pesticides.
• Skip soft, chalky or crumbly rocks.
• Do the vinegar test.
• Avoid beach rocks and coral for freshwater tanks; they're usually carbonate.

Legality and respect

Taking rocks from national parks, state parks, protected forests and private land may be against the rules. Some rivers are also protected or managed by the state. If you're not sure, ask the landowner or local authority first, and take only a few small pieces. Never take living coral or rocks from reefs; that is harmful and can be an offence. When in doubt, buy rocks sold for aquarium use.

How to Clean Batu Akuarium

1. Scrub with a stiff brush under running water. No soap or detergent.
2. Soak in a bucket of water for a day or two and check for colour or smell.
3. Optional: pour boiling water over smaller rocks to kill hitchhikers. Don't boil rocks with trapped water inside or heat them fast, as they can crack.
4. For collected rocks, a soak in a mild bleach solution (about 1:20) for an hour can disinfect them. Rinse very well, then soak in water treated with a strong dose of anti klorin.
5. Dragon stone holds a lot of clay and dust; scrub the holes and rinse until the water runs clear.

Using Rocks in an Aquascape

• Choose one rock type for a natural look. Mixing several looks messy.
• Odd numbers (3, 5, 7) and one dominant stone create a focal point.
• Bury the base a little so stones look natural rather than placed.
• Build on the glass, not on substrate, for heavy stones, so fish digging under them can't cause a collapse.
• Protect the glass with a sheet of foam or egg-crate under big rocks.
• Glue rocks together with aquarium-safe superglue gel or cyanoacrylate if you build tall structures.

Long tweezers, scissors and spatulas from the aquascaping category make it easier to plant between stones. For a full layout walkthrough, see our beginner aquascape guide.

How Much Rock Do You Need?

As a rough idea, a 2 kaki iwagumi often uses around 10–15 kg of stone, and a 3 kaki can take 20–30 kg or more, depending on style. Remember rocks add to the total weight on your stand and floor, along with water and substrate.

Rocks and Fish Compatibility

Fish	Good rock choices	Avoid
Shrimp (Caridina)	Dragon stone, lava rock	Seiryu, limestone
Livebearers, goldfish	Seiryu, smooth pebbles	Sharp lava rock with fancy goldfish
Bettas	Smooth or rounded rocks	Sharp edges that tear fins
Loaches and corydoras	Smooth river pebbles	Sharp, unstable piles
African cichlids	Limestone, holey rock, slate caves	—
Plecos	Slate caves, smooth rock	Loose stacks they can topple

Frequently Asked Questions

Batu sungai boleh guna untuk akuarium ke?

Boleh, tetapi pilih batu yang licin, tiada kesan karat dan bukan dari longkang atau kawasan industri. Buat ujian cuka; kalau berbuih, batu itu akan naikkan pH. Gosok dan rendam dulu sebelum masuk akuarium. Jangan ambil batu dari taman negara atau kawasan larangan.

Batu seiryu naikkan pH ke?

Ya, batu seiryu mengandungi kalsium karbonat dan boleh naikkan pH serta kekerasan air sedikit demi sedikit. Sesuai untuk guppy dan molly, tetapi kurang sesuai untuk udang crystal red.

Is dragon stone safe for shrimp?

Yes. Dragon stone is generally inert and widely used in shrimp tanks. Scrub out the clay dust first.

Can I put rocks from my garden into my aquarium?

Only if they pass the vinegar test, show no metal streaks, and haven't been exposed to fertiliser or pesticide. Scrub and soak them first.

Do rocks need to be boiled?

Not always. Scrubbing and soaking is usually enough for shop rocks. Boiling small collected rocks helps kill pests but can crack some stones.

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Find seiryu, dragon stone and other hardscape from Malaysian sellers on FishyHub's driftwood, rocks and stones page, and pair them with Malaysian driftwood for a natural scape.