Aquarium Decorations for Beginners

Quick Answer

Aquarium decorations make a fish tank more attractive while giving fish places to hide, rest, explore, and establish territories. Safe decorations include aquarium-approved rocks, driftwood, caves, ornaments, backgrounds, and smooth artificial plants.

Choose decorations that are non-toxic, stable, easy to clean, and appropriate for the size and behavior of your fish.

At a Glance

Why Do Fish Need Decorations?

Aquarium decorations are not only for appearance.

They can help fish by providing:

• Hiding places
• Resting areas
• Territorial boundaries
• Shelter from aggressive tank mates
• Protection for fry
• Places to explore
• Shade from bright lighting
• Natural surfaces for algae and microorganisms

A completely empty aquarium may cause some fish to feel exposed and stressed.

Decorations can make fish more confident and encourage natural behavior.

Do All Aquariums Need Decorations?

Most display aquariums benefit from some decorations.

However, certain tanks may be kept simple or nearly empty, including:

• Quarantine tanks
• Hospital tanks
• Breeding tanks
• Fry grow-out tanks
• Temporary holding tanks

These tanks are often kept simple because they are easier to clean and allow fish to be observed closely.

Even in a simple tank, a safe hiding place may help reduce stress.

Types of Aquarium Decorations

Aquarium Rocks

Rocks can create:

• Caves
• Shelves
• Territorial boundaries
• Natural-looking landscapes
• Places for plants to attach

Common aquarium rocks include:

• Slate
• Lava rock
• Dragon stone
• River rock
• Seiryu-style stone
• Aquarium-safe limestone
• Smooth decorative stone

Not every rock is suitable for every aquarium.

Some rocks may affect water hardness and pH.

Driftwood

Driftwood gives an aquarium a natural appearance and provides shelter for fish.

It may also provide:

• Grazing surfaces for plecos and shrimp
• Attachment points for plants
• Cover for shy fish
• Territorial boundaries
• Tannins that tint the water

Popular aquarium woods include:

• Mopani wood
• Malaysian driftwood
• Spider wood
• Manzanita
• Cholla wood
• Bogwood

Use wood sold for aquarium use whenever possible.

Aquarium Caves

Caves are useful for:

• Plecos
• Cichlids
• Bettas
• Kuhli loaches
• Shrimp
• Catfish
• Breeding fish
• Shy fish

Caves may be made from:

• Ceramic
• Resin
• Rock
• Coconut shells
• Clay pots
• Driftwood

Make sure openings are large enough for fish to enter and leave safely.

Artificial Plants

Artificial plants provide cover without requiring plant lighting, fertilizer, or trimming.

They are available in:

• Plastic
• Silk
• Soft fabric
• Resin

Silk or soft artificial plants are often safer for long-finned fish such as bettas.

Avoid stiff or sharp plastic plants that can tear fins.

Aquarium Backgrounds

A background is placed behind the aquarium.

It can:

• Hide cords and equipment
• Reduce reflections
• Help fish feel more secure
• Improve the appearance of the tank
• Make fish colors stand out

Simple black, dark blue, or natural backgrounds work well in many freshwater aquariums.

Decorative Ornaments

Aquarium ornaments may include:

• Castles
• Ships
• Ruins
• Statues
• Bridges
• Treasure chests
• Caves
• Cartoon-style decorations

These can be safe when they are designed for aquarium use and do not have sharp edges, small openings, peeling paint, or unstable parts.

How to Choose Safe Aquarium Decorations

A safe decoration should be:

• Non-toxic
• Intended for aquarium use
• Smooth enough not to injure fish
• Stable
• Large enough not to be swallowed
• Free from peeling paint
• Easy to inspect
• Easy to clean
• Appropriate for the fish

Before placing a decoration in the aquarium, examine every side carefully.

Run your fingers along the surface and openings.

Check for Sharp Edges

Sharp decorations can damage:

• Fins
• Scales
• Eyes
• Barbels
• Skin

Long-finned fish are especially vulnerable.

A simple test is to rub a thin piece of fabric or nylon stocking over the decoration.

If it catches or tears, the decoration may also tear a fish’s fins.

Check All Openings

Fish sometimes enter holes and become trapped.

Make sure openings are:

• Large enough for the fish to pass through
• Too small for the fish to enter
• Smooth around the edges
• Open on more than one side when possible

Avoid decorations with narrow spaces that become tighter farther inside.

Remember that fish grow.

An opening that is safe for a young fish may become dangerous later.

Avoid Unstable Decorations

Large rocks and heavy ornaments must be placed securely.

Unstable decorations can:

• Fall on fish
• Crack aquarium glass
• Crush plants
• Trap animals
• Damage heaters
• Block filter intakes

Place heavy rocks on a stable surface rather than balancing them loosely on top of gravel.

Fish that dig can remove substrate from beneath rocks and cause them to collapse.

Should Rocks Go Before or After Substrate?

Large rocks are often safer when placed directly on the aquarium bottom or on a protective base before adding substrate around them.

This prevents digging fish from undermining the rock structure.

Possible protective bases include:

• Aquarium-safe plastic grid
• Thin foam made for aquarium use
• Flat slate
• Purpose-made rock supports

Do not place extreme weight against one small point on the glass.

Can Decorations Affect Water Chemistry?

Yes.

Some rocks and substrates contain minerals that may raise:

• pH
• GH
• KH

Examples include:

• Limestone
• Crushed coral
• Shells
• Some decorative stones

These materials can be useful in hard-water aquariums but may be unsuitable for soft-water fish.

Driftwood may release tannins and sometimes lower pH slightly, especially in water with low KH.

Test the water after adding natural decorations.

How to Test Rocks With Vinegar

A basic vinegar test may help identify rocks containing carbonate minerals.

1. Place a few drops of vinegar on a dry section of the rock.
2. Watch for fizzing or bubbling.
3. Fizzing may suggest the rock can affect water hardness and pH.

This test is not perfect, but it can provide a warning.

When unsure, use rocks labeled for aquarium use.

Are Outdoor Rocks Safe?

Outdoor rocks may contain:

• Pesticides
• Fertilizer
• Oil
• Metals
• Pollutants
• Sharp edges
• Minerals that change water chemistry

Do not collect rocks near:

• Roads
• Industrial areas
• Treated lawns
• Construction sites
• Polluted waterways

Aquarium-approved rock is the safer beginner choice.

Never boil rocks. Some rocks contain trapped moisture or air and may crack or explode when heated.

Is Driftwood From Outside Safe?

Wood collected outdoors can carry:

• Pesticides
• Sap
• Mold
• Insects
• Pollutants
• Rot
• Harmful chemicals

Some woods are also toxic or decay quickly underwater.

Aquarium driftwood is safer and easier for beginners.

Avoid fresh, green, resinous, painted, treated, or pressure-treated wood.

Why Does Driftwood Float?

New driftwood may contain trapped air and may not be fully waterlogged.

To help it sink:

• Soak it in a clean container
• Weigh it down safely
• Attach it to slate
• Allow it time to become waterlogged
• Follow the supplier’s instructions

Some pieces sink within days, while others may take weeks.

Why Does Driftwood Turn the Water Brown?

Driftwood can release tannins.

Tannins may give the water a:

• Yellow tint
• Tea-colored appearance
• Brown color

This is usually not harmful to fish.

Some species naturally live in tannin-stained water.

To reduce the color:

• Soak the wood before use
• Perform water changes
• Use activated carbon when appropriate
• Use chemical filtration made for removing discoloration

Tannins may return until the wood has released most of them.

White Film on New Driftwood

New driftwood sometimes develops a white or clear film.

This is often a harmless bacterial or fungal biofilm.

It may:

• Disappear on its own
• Be eaten by shrimp or snails
• Be removed with a brush
• Return temporarily after cleaning

It is usually more unattractive than dangerous.

Should You Boil Driftwood?

Small pieces of aquarium driftwood may sometimes be simmered or soaked in hot water if the supplier says it is safe.

This can help:

• Release tannins
• Waterlog the wood
• Remove loose debris

However, large pieces may not fit safely in a pot, and boiling may damage some wood.

Never boil rocks.

Can You Use Clay Pots as Caves?

Plain, unglazed terracotta pots are commonly used in aquariums.

They can provide:

• Caves
• Breeding sites
• Hiding places
• Plant containers

Make sure the pot is:

• New or free from chemicals
• Rinsed thoroughly
• Free from sharp broken edges
• Large enough for the fish
• Stable

The drainage hole should be either safely usable or completely blocked so fish cannot become trapped.

Can You Use PVC Pipe in an Aquarium?

Plain aquarium-safe or potable-water PVC can be used for caves and shelters.

PVC is especially useful in:

• Breeding tanks
• Pleco tanks
• Quarantine tanks
• Grow-out tanks

Smooth all cut edges before use.

Avoid pipe that has been contaminated with chemicals, glue, paint, or household waste.

Are Shells Safe in Freshwater Aquariums?

Shells contain calcium carbonate and may raise:

• pH
• GH
• KH

They may be helpful in some hard-water aquariums, but they are usually unsuitable for fish requiring soft, acidic water.

Shells can also have sharp edges or small openings.

Artificial Versus Natural Decorations

Natural Decorations

Examples include rocks and driftwood.

Advantages

• Natural appearance
• Unique shapes
• Good for planted tanks
• Encourage natural behavior

Disadvantages

• May affect water chemistry
• Can release tannins
• May require soaking
• Can be heavy
• Harder to arrange safely

Artificial Decorations

Examples include resin ornaments and artificial plants.

Advantages

• Many styles available
• Usually easy to place
• Often lightweight
• Do not decay
• Require little maintenance

Disadvantages

• Paint may wear over time
• Cheap items may be sharp
• Small openings can trap fish
• Some may look less natural

Both types can work when chosen carefully.

How Many Decorations Should You Use?

There is no exact number.

The aquarium should provide enough shelter without becoming overcrowded.

Fish still need:

• Open swimming space
• Access to food
• Good water circulation
• Clear access to the surface
• Room around the filter and heater

A useful design often includes:

• Open swimming space in the front or center
• Taller decorations toward the back
• Caves or hiding places near the sides
• Enough cover for shy fish

Decorations for Territorial Fish

Territorial fish may need decorations that break up their line of sight.

Use:

• Rocks
• Driftwood
• Caves
• Tall plants
• Divided territories

This can reduce constant chasing because fish cannot see one another across the entire aquarium.

However, decorations cannot make an incompatible combination of fish safe.

Decorations for Bettas

Bettas benefit from:

• Soft plants
• Broad leaves near the surface
• Smooth caves
• Floating cover
• Gentle resting places

Avoid:

• Sharp plastic plants
• Tiny openings
• Rough resin decorations
• Strong water flow around resting areas

Bettas often rest on leaves close to the surface.

Decorations for Corydoras

Corydoras need plenty of open bottom space for feeding and foraging.

Suitable decorations include:

• Smooth rocks
• Driftwood arches
• Plants along the back and sides
• Wide caves without sharp edges

Do not cover the entire substrate with decorations.

Decorations for Kuhli Loaches

Kuhli loaches enjoy:

• Smooth caves
• Driftwood
• Leaf litter
• Dense plants
• Small safe hiding spaces

Make sure openings are safe and that the aquarium lid is secure.

Decorations for Plecos

Plecos often use:

• Driftwood
• Ceramic caves
• Slate caves
• Rock shelters
• PVC tubes

Some plecos need appropriately sized caves for breeding.

Large plecos require sturdy decorations that cannot be pushed over.

Decorations for Cichlids

Many cichlids need:

• Caves
• Rock territories
• Visual barriers
• Stable structures

Some cichlids dig heavily, so rocks must be supported securely.

African cichlid aquariums often use rock structures, while other cichlids may prefer driftwood, caves, or plants.

Decorations for Shrimp

Shrimp benefit from:

• Moss
• Cholla wood
• Driftwood
• Small caves
• Rock surfaces
• Dense plant cover

These surfaces collect biofilm that shrimp graze on.

Avoid decorations containing copper or unknown metals.

Can Decorations Block the Filter?

Yes.

Keep decorations away from:

• Filter intakes
• Filter outlets
• Air stones
• Heater controls
• Thermometers

Blocking circulation can create areas where waste collects.

Make sure water can move around the aquarium.

Keep Decorations Away From the Heater

Decorations should not:

• Press against the heater
• Block water circulation around it
• Trap fish beside it
• Prevent you from seeing its indicator light
• Cause the heater to rest against substrate or glass improperly

Follow the heater manufacturer’s clearance instructions.

How to Clean Aquarium Decorations

During routine maintenance:

1. Remove loose debris with a gravel vacuum.
2. Gently brush algae from accessible surfaces.
3. Rinse removable decorations in old aquarium water when needed.
4. Return them without disturbing the aquarium excessively.

Do not use:

• Soap
• Detergent
• Household cleaners
• Furniture polish
• Scented products

For stubborn algae, clean only a few decorations at a time so the aquarium is not completely disturbed.

Should You Remove All Decorations While Cleaning?

Usually, no.

Removing everything at once can:

• Stress fish
• Destroy territories
• Disturb plants
• Release trapped waste
• Remove some beneficial bacteria
• Cause aggression when decorations are returned

Clean only what is necessary.

When Should a Decoration Be Replaced?

Replace a decoration when it has:

• Peeling paint
• Cracks
• Sharp exposed edges
• Rust
• Loose pieces
• A strong chemical smell
• Openings that are no longer safe
• Damage that cannot be repaired safely

Inspect decorations regularly as fish grow.

Common Beginner Mistakes

• Using decorations not made for aquariums
• Adding sharp plastic plants
• Balancing rocks insecurely
• Creating holes that trap fish
• Boiling rocks
• Using painted household objects
• Adding too many decorations
• Blocking the filter intake
• Placing decorations against the heater
• Using shells without considering water hardness
• Collecting polluted outdoor wood or rocks
• Removing every decoration during each cleaning
• Forgetting that fish grow larger

Rick’s Experience

During my years keeping and breeding tropical fish and owning the FinTastik Tropical Fish store, I saw many fish become more comfortable once they had proper cover and hiding places.

Decorations should make the tank safer, not more dangerous. I always recommend checking every opening, edge, and rock structure before adding fish.

Frequently Asked Questions

Can I put household decorations in an aquarium?

Only use an item when you know it is non-toxic, waterproof, free from metals, and safe for continuous aquarium use. Aquarium-approved decorations are the safest choice.

Can aquarium decorations hurt fish?

Yes. Sharp edges, small openings, unstable rocks, peeling paint, and rough surfaces can injure fish.

Do fish like heavily decorated tanks?

Some fish prefer heavy cover, while active swimmers need more open space. Match the layout to the species.

Can I use LEGO bricks in an aquarium?

LEGO pieces are not sold as aquarium decorations. Although some hobbyists use certain plastic pieces, aquarium-approved decorations are the safer beginner choice.

Can I use ceramic mugs or dishes?

Some plain food-safe ceramics may be usable, but glazes, paints, metallic trim, and cracks can create risks. Aquarium caves are safer.

Why is my driftwood covered in white slime?

New driftwood often develops harmless biofilm. It usually disappears over time or can be gently removed.

Should I glue aquarium rocks together?

Aquarium-safe silicone or adhesive may be used when appropriate. Make sure it is fully cured before placing it in the aquarium.

Can decorations reduce fish aggression?

Decorations can break up sight lines and create territories, but they cannot fix severe overcrowding or incompatible fish.

Can I change the decorations after fish are added?

Yes. Make changes gradually and avoid trapping or frightening the fish.

Rick Recommends

Useful decoration supplies include:

• Aquarium-safe driftwood
• Smooth aquarium rocks
• Ceramic caves
• Soft artificial plants
• Aquarium background
• Aquarium-safe silicone
• Algae brush
• Gravel vacuum
• Water test kit

Related Articles

• Aquarium Equipment Guide
• Aquarium Substrates for Beginners
• Aquarium Lighting for Beginners
• Aquarium Filters for Beginners
• Aquarium Heaters for Beginners
• Aquarium Thermometers
• Aquarium Gravel Vacuums for Beginners

Final Thoughts

Aquarium decorations should make the tank attractive while also improving the environment for the fish. Choose safe materials, provide suitable hiding places, keep structures stable, and leave enough open swimming space.

Always inspect decorations for sharp edges, dangerous openings, peeling paint, and unstable parts before placing them in the aquarium.