Japanese Volcanic Lava Rock from Dōgo Island

As a welfare first orientated Medaka keeper and breeder, I’m very particular about the materials I use in my tubs and display systems.and that's exactly why we have decided to collaborate with REEF&ROCK.

This listing is for authentic black volcanic lava rock sourced directly from the volcanic landscape of Dōgo Island in Japan’s Oki archipelago, which is a UNESCO recognised region, and one of the most respected geological sources of high quality aquascaping stone.

These lava rocks were sourced under license and hand harvested in limited amounts to ensure the higest quality with minimal environmental impact in support of local conservation efforts.

In addition this batch has independent laboratory analysis which has been conducted by X‑Ray Minerals (UK) using XRD/XRF to confirm geological origin, purity, and full inertness.

For Medaka, this stone is truly exceptional. The deep rich matte black colour and natural shaping mirror the shallow creeks, rice field channels, and coastal inlets where wild Medaka have lived for centuries. In tubs, the contrast brings out colour in every strain.

The vesicular surface is naturally micro‑pitted, which encourages biofilm development and plant anchoring. This is exactly what fry graze on in outdoor systems, and it’s one of the reasons these stones work so well for stable, mature tubs. They’re lightweight enough to position easily, yet structurally strong enough for stacked or architectural layouts.

Chemically, the rock is completely inert. It will not alter pH, GH, KH, or TDS, making it ideal for sensitive strains, breeding groups, and long‑term outdoor tubs.

Every box contains a unique mix of stones shaped by volcanic activity. No two pieces are the same, and each one adds genuine Japanese character to a setup.

Why I Recommend These Lava Rocks for Medaka:

• Perfect for traditional Medaka tubs and Japanese style water gardens  

• Enhances colour and behaviour in outdoor displays  

• Provides natural structure, shelter, and visual complexity  

• Supports biofilm growth for fry and juvenile grazing  

• Fully inert — maintains stable water chemistry year‑round  

• Ideal for heritage strains, selective breeding, and display tanks  

• Authentic Japanese provenance for keepers who value cultural accuracy

Perfect For:

• Medaka tubs (indoor and outdoor)  

• Heritage Japanese biotopes  

• Patio ponds and shallow water gardens  

• Aquascapes (Iwagumi, Nature Style)  

• Freshwater and marine aquariums  

• Terrariums, paludariums, and vivariums  

• Bonsai, Wabi‑Kusa, and plant displays  

• Natural décor and landscape projects

Lab Verification Summary:

Independent XRD/XRF analysis confirms:

• Fully inert basaltic composition  

• No harmful contaminants  

• Stable mineral profile suitable for aquatic use  

• Major oxides dominated by SiO₂, Al₂O₃, Fe₂O₃, CaO, MgO  

• Trace elements within safe natural ranges  

• No detectable arsenic, selenium, germanium, molybdenum, tin, antimony, cesium, or uranium  

(Full laboratory report available on request.)

Details:

Total weight: 2kg approx 

• Average stone size: 8 - 15 cm (3 - 6 inches)

• Average count: 4 rocks per box

• Mixed natural shapes and textures, hand selected for quality

Total Weight: 5kg approx 

• Average stone size: 8 - 15 cm (3 - 6 inches)

• Average count: 6 - 10 rocks per box

• Mixed natural shapes and textures, hand selected for quality

Other quantities are available - pls contact to discuss rock sizes, costs etc for custom orders