Hardscape Materials
Rock & Wood Compared
Hardscape — rock and driftwood — is the structural skeleton of every aquascape. Choosing the wrong materials can alter water chemistry, harm fish, and undermine your design. This guide covers every major type used in UK freshwater aquariums.
By Hasan, Aquascaping Lead, AD Aquatics · Updated 2025
Aquascaping Rock Types
| Rock Type | Visual Character | pH Effect | KH Effect | Best Style | Suitable Species | UK Availability |
|---|---|---|---|---|---|---|
| Seiryu Stone | Grey/blue with white calcite veining; angular, dramatic | Raises pH slightly over time | Raises KH (contains calcium carbonate) | Iwagumi, Nature Aquarium | African cichlids, livebearers, community fish; avoid discus/softwater species | Widely available; £5–15/kg |
| Ohko / Dragon Stone | Warm earth tones; rough, pitted texture; organic shapes | Minimal to none | Minimal to none | Nature Aquarium, jungle | All freshwater species; excellent for softwater setups | Widely available; £8–18/kg |
| Lava Rock | Black/red; highly porous; rough texture; industrial look | None | None | Biotope, cichlid caves, background | All; excellent for cichlid cave structures | Very widely available; £3–8/kg |
| Limestone / Tufa | Off-white, cream; rough; holey texture (tufa); stacks well | Raises pH significantly | Raises KH significantly | African cichlid tanks; Tanganyika biotopes | African cichlids only — dangerous for softwater species; can push pH above 8.5 | Widely available; £3–10/kg |
| Slate | Dark grey/black; flat planes; geometric stacking | None | None | Modern, geometric, cichlid tanks | All freshwater species | Very widely available; cheapest option; garden centres |
| Seiryu (fake/resin) | Replicates Seiryu appearance | None | None | Where water chemistry control is critical | All; useful for softwater species wanting Seiryu aesthetic | Available from specialist retailers; £10–20/kg |
| Quartz / River Stone | Smooth, rounded; natural white/grey/brown | None | None (unless limestone-containing) | Natural river biotopes, SA blackwater | All; avoid limestone-containing quartzite | Garden centres, beaches (check local rules); very cheap |
Test unknown rocks with white vinegar — if they fizz, they contain calcium carbonate and will raise KH and pH. Always test water chemistry after adding new rock.
Aquascaping Driftwood Types
| Wood Type | Visual Character | pH/Tannin Effect | Durability | Best Style | Notes | UK Availability |
|---|---|---|---|---|---|---|
| Spider Wood | Thin, branching; complex fine structure; pale grey-brown | Low tannins; slight pH reduction | Medium — can soften over years | Nature Aquarium, jungle, planted tanks | Lightweight; may need anchoring with rocks; excellent for moss attachment | Widely available; £8–30 per piece |
| Manzanita Wood | Twisted branches; red-brown bark; elegant organic shapes | Low; minimal tannins | Very high — durable for many years | Nature Aquarium, biotope, showpiece | Sinks quickly; easy to work with; plants attach well | Available from specialist retailers; £15–60+ per piece |
| Malaysian Driftwood | Smooth, curved; dark brown; solid large pieces | High tannins — stains water brown for weeks; lowers pH | Very high | Blackwater biotope, jungle | Pre-soak for 1–2 weeks to reduce tannin release; use activated carbon if water clarity desired; tannins beneficial for softwater/discus setups | Very widely available; £5–25 per piece |
| Bogwood | Dense, rounded; dark brown-black; natural appearance | Moderate tannins; reduces pH | Very high — ancient preserved wood | Biotope, jungle, SA blackwater | May release tannins for extended periods; dense and sinks naturally | Widely available; £5–20 per piece |
| Cholla Wood | Cylindrical skeleton of cactus; hollow with mesh-like structure | Minimal; slight tannins | Low — decomposes over 6–18 months | Shrimp tanks, small biotopes | Excellent biofilm surface for shrimps; decomposition adds organic matter — replace periodically | Available from shrimp/nano retailers; £3–10 |
| Redmoor Root | Fine tangled root structure; warm red-brown tones | Low–moderate tannins | Medium–high | Nature Aquarium, biotope | Very popular in planted tanks; create naturalistic root tangles; pre-soak recommended | Widely available in UK; £10–40 per piece |
How to Prepare Hardscape Safely
Rock preparation
- Scrub with a stiff brush in clean (untreated) water to remove dust and organic matter
- Test unknown rocks for calcium carbonate with white vinegar — fizzing indicates KH/pH impact
- Never use soap, bleach or chemicals — impossible to rinse completely from porous rock
- Boiling small rocks is optional but adds no significant benefit for hard, non-porous types
Wood preparation
- Soak in a bucket of clean water for 1–4 weeks, changing water every 2–3 days — reduces tannin release and ensures the wood is waterlogged enough to sink
- Boiling for 1–2 hours accelerates tannin extraction and kills surface pathogens — recommended for pieces added to fish tanks with sensitive species
- Secure floating wood with rocks, slate plates, or stainless-steel screws — standard zinc-coated screws corrode in water and release harmful zinc ions
Frequently Asked Questions
Does Seiryu stone raise pH?
Yes — Seiryu stone contains calcium carbonate (calcite veins) which slowly dissolves in water, raising KH and pH over time. In a well-buffered tank this effect is gradual, but in a low-KH softwater setup it can push pH significantly upward. Use resin Seiryu alternatives, Dragon Stone (Ohko), or inert rocks if keeping softwater species like discus or cardinal tetras.
Why is my tank water brown after adding driftwood?
Brown water is caused by tannins leaching from the wood — this is natural and harmless (it mimics blackwater conditions), and beneficial for softwater/acidic species. To clear it: soak or boil wood before adding, run activated carbon for 2–4 weeks, and do regular water changes. Tannins diminish over time even without treatment. They lower pH slightly — useful for softwater setups, potentially problematic for hardwater/cichlid tanks.
What hardscape is best for African cichlid tanks?
Limestone, tufa rock, and lava rock are the three primary materials for African cichlid hardscapes. Tufa's holey structure creates natural-looking cave systems; limestone stacks well and raises KH beneficially for cichlids; lava rock is inert but creates excellent caves. Avoid acidic wood (tannins lower pH) in cichlid tanks. See our African cichlid care guide for full setup guidance.
Want expert hardscape design?
Hasan sources and arranges hardscape for every AD Aquatics installation — selecting materials appropriate to your water chemistry, species and visual style.