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Aquarium Decorations

Decorations make an aquarium look natural and give fish places to hide, explore and claim territory. This guide explains which decorations are safe, how rocks and wood change water chemistry, simple aquascaping layouts, and what to check before buying anything for your tank.

What makes an aquarium decoration safe

• Aquarium-safe materials — decorations sold for aquariums are made from inert resin, ceramic or glass, or from natural materials such as rock and wood that are suitable for water.
• No sharp edges — long-finned fish such as bettas and fancy goldfish tear fins easily; run a pair of tights over ornaments and discard anything that snags.
• No toxic coatings — avoid painted household ornaments, metal objects, treated wood and anything with glitter or glue not made for aquariums.
• No traps — holes and tunnels should be large enough that fish cannot get stuck.
• Stable placement — heavy rocks should rest on the glass bottom, not on top of gravel, so burrowing fish cannot undermine them.

Types of aquarium decorations

Compare products in each category at aquarium caves and hides, aquarium driftwood, aquarium rock and silk aquarium plants.

How decorations affect water chemistry

Most resin and ceramic ornaments are inert, but natural materials can change the water. Limestone, marble, coral and shells dissolve slowly and raise pH and carbonate hardness — useful for African cichlid tanks, but not for soft-water species such as tetras and discus. A simple test is to drop vinegar on a dry rock: fizzing indicates carbonates. Driftwood releases tannins that lower pH slightly and stain the water tea-coloured, which many South American fish tolerate or even prefer. Soak and rinse new wood for several days, changing the water, to reduce staining; activated carbon in the filter also removes the colour.

Aquascaping basics for a natural look

1. Choose one type of rock and one type of wood so the scape looks coherent.
2. Use the rule of thirds: place the main focal point — a large rock or piece of wood — about one third from one side, not in the centre.
3. Build height at the back and sides and leave open swimming space at the front.
4. Slope the substrate from about 2 inches at the front to 3–4 inches at the back to create depth.
5. Group smaller rocks around the main stone to look like a natural outcrop.
6. Add plants in odd-numbered clusters, taller species behind shorter ones.

Popular styles include the “nature aquarium” with flowing, landscape-like layouts; the “iwagumi” built around a few carefully placed stones; and biotope tanks that recreate a specific river or lake habitat.

Decorating for your fish

• Bettas — soft silk plants, smooth caves and a leaf hammock near the surface.
• Cichlids — piles of rock with caves to establish territories; secure them against digging.
• Bottom dwellers (corydoras, loaches) — smooth sand or fine gravel and caves.
• Plecos — driftwood to rasp on and caves to shelter in.
• Shrimp — moss, leaf litter and fine structures to graze on.
• Goldfish — robust, smooth decorations and plenty of open space; they uproot delicate plants.

Preparing new decorations

Rinse new ornaments in plain water — no soap or household cleaners. Scrub natural rock with a brush. Boil or soak driftwood to help it sink and to remove loose tannins. If you collect rocks yourself, avoid anything from polluted sites, and check local rules before taking wood or stone from nature. Never use decorations that previously held chemicals or that came from another tank with disease without cleaning them thoroughly.

Cleaning decorations

Algae naturally grows on decorations. Scrub ornaments with a soft brush during water changes, using tank water so you do not remove all the beneficial bacteria living on surfaces. For stubborn algae, remove the decoration and scrub in a bucket of old tank water. Avoid bleach unless you rinse and dechlorinate extremely thoroughly, and never clean everything at once — keep some established surfaces to protect the biological balance.

How much decoration is too much?

Enough decoration gives every fish a hiding place and breaks lines of sight, which reduces stress and aggression, especially in cichlid and community tanks. Too much crowds swimming space, traps debris where the filter cannot reach and makes cleaning hard. A good rule is to leave roughly a third to a half of the tank as open water, and to make sure you can reach behind and under large pieces with a siphon.