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Author: Andy Gordon and Michelle Stuart
Title:  Tank Decor

Summary:  A description of the different substrates, woods, and decorations used in aquaria. Their advantages and disadvantages.
Contact for editing purposes:
email: Michelle Stuart:
Date first published: 2003

Publication: Andy and Michelle's web site:
Reprinted from Aquarticles:
Internet publication (club or non-profit web site):

1. Credit author, original publication, and Aquarticles.
2.  Link to  and original website if applicable.
3.  Advise Aquarticles
Printed publication:
Mail THREE  printed copies to:
#205 - 5525 West Boulevard
Vancouver, British Columbia
V6M 3W6

We will forward one each to Andy and Michelle.

Tank Decor

by Andy Gordon of England, and Michelle Stuart of Ontario Canada
Reprinted, with permission, from their web site

Tank decor.jpg (19526 bytes)
Malawi Mbuna like this young male Labeotropheus trewavase need a very rocky environment to feel comfortable and look their best.
Photo by Andy Gordon

Almost every tank whatever type it is needs some decoration to make it look more pleasing and to give the livestock a more natural setting and somewhere to hide. From the substrate up there are thousands of variations and endless possibilities available to us. But what is safe, what looks good, what are its disadvantages - in other words what can we use to decorate our tanks with safely?


Plain gravel
Probably the most common substrate used, but care should still be taken when choosing it.
- Make sure it isn't too sharp, the more rounded it is the better so that any bottom living fish like loaches or Corydoras don't end up injuring them selves on it. It isn't uncommon to see Corydoras catfish with their barbels worn away due to rough gravel and this will shorten their lives considerably and prevent them from breeding - strange as it sounds because male corys use their barbels in courtship.
- The size of the gravel is important too, especially if plants are going to be grown or an under-gravel filter is used. The best size is 1 to 2 mm, at this size it will not compact and become anaerobic too easily, and plants find it easy to root in.
- Make sure the gravel doesn't contain any calcareous material like limestone, shells, coral fragments etc. because these will raise the pH and hardness of the water. For most tropical fish this would be undesirable but there are a few which prefer such conditions, and that is why it is important to know what your fish require before buying them.
- Plain gravel has no effect on the water chemistry.

Silica Sand
Is also very popular and makes a good substrate for keeping many bottom living fish. And always looks fresh and clean.
- The sand is prone to become compact when it is kept too deep and that will lead to problems.
- It can be used below gravel and when used this way it makes a great place for plants to root.
- The sand is very pale and if used in a sparsely decorated tank with bright lighting it will make the fish look washed out.

River Sand
Worth seeking out due to its very natural looks
- This is a great substrate because it is a little more coarse than silica sand so it is less likely to compact and it looks great.
- It has no effect on the water chemistry.

Coral Sand
This is only suitable for marine and hard alkaline systems.
- This substrate looks very clean and makes other decor and tank occupants stand out.
- It will buffer the water and prevent pH drop to some extent.
- Because it is so pale it could make the fish appear washed out and not show them to their best.
- It will alter the water's chemistry by making it harder and by raising the pH.

- Finer than coral sand and maintains the pH in marine aquariums more effectively.

This is another specialist substrate. For soft acidic water tanks.
- An excellent substrate for some killifish, apistogrammas and some characins where soft acidic water is required.
- Substrate spawning killifish will use it to breed in and the eggs can be kept in it through a dry spell if necessary.
-  If there is any turbulence the bits of peat will remain in suspension and look a mess.
- It will affect the water chemistry by softening the water and lowering the pH.
- In time it will discolour the water making it an amber colour.

Substrate additives
Mainly used to feed plants or to help maintain the water chemistry.
- Calcium plus - Helps maintain a high pH.
- Fluorite - A plant food additive rich in iron. Needs to be mixed with other substrate and buried below a layer of gravel. It may discolour the water initially but do not rinse it before use or you will shorten its effective life.
- Laterite - Used like fluorite, many people I know have said it is better and cleaner to use.

Rocks and Stones

There are a lot of stones to avoid in the fish tank, these include - Ores (rocks containing metal), and Calcareous (rocks containing Calcium) shouldn't generally be used for fresh water tanks.

Pale grey in colour, suitable for all tanks.
- Completely inert and is cheap to buy. Large thin pieces can be used as a background.
- Beware of sharp edges.

Too heavy and will raise the pH. Not recommended.

Varies in shades of golden brown. Inert.
- Water-worn pebbles of varying sizes can give a very natural look to an aquarium.
- Completely safe to use for all tanks after a simple rinse.
- Can be used to construct caves etc.

Tufa Rock
Marine and African cichlid tanks only.
- A very light rock so excellent where a lot of rock is needed for building a reef.
- Very soft and easily made into different shapes, or cut.
- It is formed from Magnesium Sulphate so it will harden the water.
- Very cheap to buy - more so if you get it from garden centres instead of fish shops.

- Safe and completely inert.
- Can be sharp and is harder than glass - making it able to scratch the glass if it is near to it or is knocked against it.
- Doesn't look very natural.

Dead Coral
Marine tanks only. Not Recommended
- Due to poor collection and reef destruction this is an ethically poor tank decor and illegal in some countries.
- Realistic artificial pieces are now widely available and a much better choice.

Live Rock
Marine Tanks only
- Cured live rock looks great in a marine tank by making it as natural as possible.
- It can provide a very good biological filter.
- Lots of marine life will be added to the tank with it.
- Some of the above life may be undesirable

Volcanic Rock
- Completely inert.
- Very light.
- Needs to be mixed with rounded stones because it is too rough for fish to use for spawning.
- It has an unnatural purple colour when new, but it soon naturalises.


- Very natural and safe to use.
- Needs to be soaked for a few weeks to become waterlogged so that it sinks.

- Very popular and widely available.
- It will colour the water initially, this can be reduced by boiling in water before use.
- Heavy enough to sink without any help.
- It will acidify the water so keep an eye on the pH when it is used, particularly at the beginning.

Mopani wood
- One of the hardest most dense woods in nature.
- Will sink like a stone unaided.
- It will initially colour the water but it won't affect the water chemistry greatly.
- It is naturally very gnarly and it has dark and pale streaks running through it.
- Can be expensive.

Green wood
Not recommended
- Live wood or recently chopped wood is best avoided.
- It will still contain sugars and starches, and as these breakdown the free oxygen in the water will be reduced.
- It may also contain toxins which are the trees' natural defence.

Artificial Wood
- Very realistic and safe to use.
- Can be limited in size.
- Expensive.


Real Plants
More details elsewhere

Artificial Plants
- There are two main types of artificial plants available, material and plastic.
- Both suffer from algae eventually.
- The material leaves move more realistically in the water but they aren't as robust as the plastic ones.
- There is a whole range of very realistic looking plants available today.
- They have a very long lifetime.

To clean them periodically, simply soak them in a weak bleach and water solution for an hour, followed by several very good rinses. Keep rinsing until there is no detectable odour of bleach. In the final rinse let them soak in a bucket of water to which some dechlorinator has been added. Bleach will kill the fish if it is allowed to get into the aquarium. If in doubt rinse again.

Other Items

Terracotta Pots
- Don't use new terracotta - lime is added during manufacture and it will affect the water chemistry.
- Old weathered terracotta is entirely safe after a quick rinse.
- They make excellent caves for breeding dwarf cichlids.
- Oddly, they look surprisingly natural.

Sea Shells
Marine and African cichlid aquaria only.
- Add a little authenticity to a marine tank.
- Essential when hermit crabs are being cared for.
- Essential for when Lake Tanganyikan shell dwellers are being kept and/or bred.
- They will harden the water if there are enough present, don't use in acidic water.

Coloured gravels
- If these are to your taste then use them. The fish won't notice in most cases.
- Popular with children.
- Captive bred fish will have been raised in vats void of any decor and a natural looking tank will look every bit as foreign to them as a multi-coloured artificial setting.

Coloured Glass Pebbles
As above.

As above.

- Amazingly these are available for fish tanks.
- I am speechless.
- I can only imagine that a moving or flashing coloured light will frighten most fish.

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