Rocks in your aquarium are a bit like furniture in your living room: they add ambiance, character, and complete the look. But… just like you wouldn't put a dirty secondhand sofa in your house without cleaning it, you wouldn't want to just throw a random pebble into your tank. There are quite a few myths about "toxic" rocks and bizarre cleaning rituals (yes, people really do boil rocks 🙈). Time to clear things up.
Most natural stones are safe for aquariums. Rinse them well with tap water, avoid calcareous or metallic stones like limestone, malachite, and azurite, always place them on a layer of sand or gravel, and test the pH if you have any doubts. Simple, right?
Which rocks are safe for your aquarium?
There's no secret list of magical aquarium rocks—most natural rocks are perfectly safe as long as you know what they do to your water. However, there are a few exceptions and popular choices among aquascapers:
- Calcareous stones (fizzing with vinegar) increase pH and GH. Ideal for African cichlids, less so for planted tanks.
- Avoid malachite & azurite : these contain copper, which can be toxic to fish and shrimp.
- Coated shop stones may have an oily residue — rinse well with a drop of dish soap and rinse thoroughly.
- Metallic glint? Try the vinegar test: if it fizzes, the stone contains lime and can affect water parameters.
Popular and safe aquarium stones (Aquania selection)
Below you'll find an overview of safe, decorative stones commonly used in aquascaping — all available at Aquania.nl :
| Stone type | Properties | pH effect | Usage tips |
|---|---|---|---|
| Dragon Stone (Ohko) | Brown-green textured stone with irregular shapes, ideal for natural landscapes. | Neutral – slightly basic, very mild effect. | Popular for planters; rinse well before use. |
| Hakkai Stone | Dark gray, smooth stone with soft lines, perfect for minimalist layouts. | Neutral. | Perfect for calm hardscapes; stable and easily stackable. |
| Lava Stone (Premium) | Lightweight, porous lava rock – promotes bacterial growth and filtering action. | Neutral. | Ideal for hardscape base or as filter material. |
| Mini Landscape Stone | Gray-blue stone with a mountainous pattern, similar to Seiryu. | Slightly pH-increasing (limescale traces). | Popular in Iwagumi style; combine with ground cover plants. |
| Glimmer Wood Rock | Unique blend of stone and wood texture; gives a natural look. | Neutral. | Combine with wood types or moss for extra contrast. |
| Slate | Flat, layered stone – ideal for sheltered areas or patios. | Neutral. | Perfect for shrimp and cichlid tanks; can be easily broken to size. |
| Fossilized Wood | Petrified wood with warm colours and natural textures. | Neutral – sometimes slightly pH-raising. | Gives a natural, warm look to your aquarium. |
| Knife Stone | Dark gray stone with sharp lines and high contrast. | Neutral. | Ideal for aquascapes with strong compositions and height differences. |
| Maple Leaf Rock | Light brown, rocky stone with veins like a leaf structure. | Neutral. | Beautiful in natural style scapes with sand or plants. |
| Gobi Rock | Warm, ochre-coloured stone with rounded shapes. | Neutral. | Perfect for desert aquascapes or dry biotopes. |
| Fairyland Stone | Light gray, open structure with soft tones – fairytale appearance. | Neutral. | Popular in artistic aquascapes with light colour contrast. |
| Leopard Stone | Beige to gray with unique spot patterns. | Neutral. | Decorative and stable; combines well with sandy soil. |
| Light Pagoda Stone | Light brown layered stone, resembles ancient pagoda temples. | Neutral – slightly pH-raising. | Perfect for elevation changes and dynamic layouts. |
| Zen Pebbles | Rounded pebbles with smooth surface. | Neutral. | Ideal for fish like Corydoras; safe and natural. |
How do you clean and prepare aquarium stones for use?
- Choose safe rock types: use only rocks that are suitable for aquariums (as above).
- Rinsing & brushing: running a tap with a brush is sufficient – boiling or baking is unnecessary and risky.
- Vinegar test: Test for limescale if you are unsure whether the stone is inert.
- Check stability: place stones on sand or gravel to prevent glass breakage.
- pH check: measure your water values a few days after installation.
Common Mistakes (and How to Avoid Them)
- Cooking everything for fear of illness: not necessary; just rinse well.
- Using sharp stones: can damage fins or bellies; choose smooth varieties.
- When placing heavy rocks directly on glass, always first apply a layer of sand or gravel.
- Failure to check stability: heavy stones may shift – test this before filling.
Checklist: safe aquarium stones
- ✅ Safe varieties selected (Dragon, Lava, Hakkai, Mini Landscape, Slate, Zen Pebbles, etc.)
- ✅ Vinegar test performed when in doubt
- ✅ Clean and without oil or dust layer
- ✅ Stably placed on sand or gravel
- ✅ Water values checked after installation
Conclusion: what are the best stones for your aquarium?
Most rocks are perfectly safe for your aquarium, as long as you clean them thoroughly, inspect them, and place them wisely. Dragon Stone, Lava Stone, and Hakkai are popular choices because they're neutral and have a natural look. Avoid rocks with a chalky or metallic sheen, and always apply a protective layer under your hardscape. Need help choosing rocks for your scape? Feel free to send me a message – I'd be happy to help! 😉
Read more: The Walstad Method
Product tip(s): View all aquarium stones Wood for aquascaping
