Our article came about through questions from my working colleagues as to exactly what decorative materials they could use in order to embellish the look of their aquarium(s).

Before adding any of the décor we will feature it is a good idea to take the time to draw a plan of how you wish your aquarium to look; you will be surprised at how this will save time and help to determine the preparation of the finished setup.

Rocks and stones

Cobbles and pebbles - can give your aquarium a freshwater/riverbed type effect.

Lava rock - can be used in large pieces to create a different look.

If you want, you can also make a backdrop effect that is suitable for growing plants such as Anubias (usually Anubias barteri var. nana) or Java Fern (Microsorium pteropus), as the roots of the plants should be able to anchor themselves securely onto the open-pored structure of the lava rock.
Broken pieces or chunks (remember to remove any sharp edges or corners which may injure livestock) look very effective when spread around the aquarium.

West Moorland rock - although it can be expensive to purchase, this rock has an attractive reddish colour with markings that make it worth buying. Some of my friends use this rock in brackish setups.

Coal - I tend to avoid the use of coal, as it can be a little messy to use and needs to be thoroughly washed before adding to an aquarium. However, it makes a good medium for dark-based displays, e.g. highlighting the colours of Blind Cave Characins (Astyanax fasciatus mexicanus), and has the advantage of sucking nitrites/nitrates and other aquarium waste products into its porous structure. Thus, as the coal is periodically removed and replaced with new pieces, out go these undesirable elements.

Slate - I use slate as it really stands out in aquaria giving an outstanding and natural look. Pieces joined together make excellent caves - my local pet shop owner always recommends flat-purple pieces as suitable for this particular task. This is another good material that can be used to form a cavern look (enhanced through the use of red lighting) in order to show the colours of Blind Cave Characins to their full effect.

Granite/Sandstone/Flint - All are inert rocks suitable for aquarium use. Granite adds a sparkling effect to aquaria.

Substrate medium

Gravel – Different colours are available so it is down to personal preference. I prefer natural-pea gravel to give the regular or natural look. Special gravel cleaners keep the gravel free of compacted mulm.

Some fish, like the Red Giant Gourami (Osphronemus sp), enjoy moving gravel

Sand - Use inert sand that is fine and nicely coloured. Choose the right sand for the right setup.

Some fish can make a sandstorm by wriggling about in the sand, which upsets the other fish and the aquarium itself. I personally avoid using sand but should you wish to have a go I advise the use of only a thin layer.
Excellent medium for Corydoras, as it protects their barbels (whiskers) from ware, and for burying Akysis catfish.

Coral and coral sands

Slowly dissolves making water hard and alkaline. This is fine for use in Goldfish aquaria, as these particular fish can handle hard water conditions, but beware as sharp coral can damage sensitive mouthparts. Brilliant for use in Rift Valley Cichlid setups, as these fish come from naturally hard water lakes, but to be avoided with most other tropical freshwater species as their habitats tend to be more acidic to neutral in nature.
Worth watching out for are the artificial corals available at many aquatic retail outlets.

Shells

Seashells - Slowly dissolve in water thus making water alkaline, but a few small shells will not make much of a difference.

Escargot shells- Provide cover and breeding places for certain dwarf Rift Valley Cichlids.

Wood

Bamboo shoots - Before proceeding with Bamboo read my article on the Ryedale Aquarist Society website. You may be able to acquire Bamboo shoots that have already been coated to prevent rotting (ask before buying).

Bogwood - The most popular wood used in aquaria. It provides lignin (which aids digestion) and releases tannin (see the article by Gerry Hawksby and David Marshall on the Northern Tropicals website) that gives the aquarium an Amazonian type effect.

Mopani - A wood sourced from Africa. Releases less tannin than bogwood. This wood is harder, tends to be more interestingly shaped and is light in colour.

Bogwood and plants show off the colours of these
Red-bellied Piranha (Pygocentrus cariba) to perfection

Plants

Both plastic (which have the advantage of not been used as a food source by your fish) and live plants (which reduce algae and produce oxygen) are available from aquatic retail outlets. A combination of both can make a great attraction for your aquarium.

Ornaments

Plenty of variety including plastic and stone types. Of great use are airpump driven aeration ornaments, such as boats and spinning wheels, which not only provide extra oxygen but also add multiple bubbles that make the aquarium look more attractive.

Background décor

Avoid painting the back of your aquarium and use the background sheets, cut to size, available from aquatic retail outlets. Those with double-sided designs allow you to alternate the desired background.

This rock escarpment background shows both plants and fish
(Red Wagtail Platy, Xiphophorus maculatus) off perfectly.

Collecting material from outside

Unless you are experienced in collecting your own aquarium décor please restrain from collecting stones and rocks etc. from your garden, water sources, (where toxins are diluted by the large volume of water passing over rocks etc.) and other 'natural sources' as these may carry with them toxins which, when released, may well alter water chemistry/quality and affect livestock in your aquarium.

In conclusion

It is best to purchase whatever material you require from local aquatic retail outlets as, with the main exception of woods, most will have been treated in order to be safe for aquarium use.