How to Decorate Your Aquarium

Fishes’ surroundings are important to their safety in nature, and to their psychological well-being in captivity. This, and not what you think looks ‘nice’, must be your prime consideration. In the unlikely event that your fish ask you to match the room decor to theirs, then, and only then, will you be justified in asking them to accept blue gravel to match the curtains! The fish are an integral component of your pleasing underwater mini-world, and if they are unwell, unhappy, or dead, then decor that matches yours will be small consolation.

Unless you are reasonably confident in your geological and/or botanical knowledge, you should avoid collecting your own decor, and buy from an aquarium dealer, where you may have some legal redress if it proves unsuitable. Rocks are expensive, however, and you may find it beneficial to learn a little geology.



The aquarium decor is divided into three parts: substrate, background and internal decor’ such as rockwork and plants. Many people don’t regard the substrate as important, and forget about the background entirely – serious errors indeed.

The substrate

The substrate is the term used to describe the material found on the bottom of both a biotope and an aquarium, from the point of view of the aquarist it is useful for planting vegetation and bedding rocks securely, and nicer to look tit than bare glass. The fishes probably also prefer to have a substrate for this reason, and some like to move it around as a preliminary to breeding or as part of their normal feeding behaviour.

The substrate should be chosen to accord with the required water chemistry: coral sand or gravel for the reel aquarium; hardness-free gravel or sand for soft water biotopes; tiny nontoxic sand or gravel for hard water/brackish aquaria, perhaps with some coral sand or limestone chips added to buffer the pH.

If possible, avoid light-reflective substrates for fresh- and brackish-water fish, especially those from biotopes which typically have a dark (leaf litter) bottom. If the fish needs to dig, provide gravel it can move, not small pebbles – and if digging or sifting is likely, avoid sharp-edged materials. This also applies for fish that rest on the bottom, or ’scan’ it with delicate sensory barbels.

Artificially colored gravels are unnatural, expensive and potentially unsafe. Although they sometimes have a plastic coating to prevent leaching of dye into the water, plastics – particularly thin coatings – do not last forever, especially if churned around by fish or immersed in acidic or salt water.

The background

Most of the fish we keep arc relatively small, and tend, in Nature, to remain close to the shelter of the bank or reef in order to be able to take cover and avoid being eaten. The aquarium should normally simulate an area of lake or river bank, or a part of the reef wall, not the open spaces of the main stream, lake centre, or open sea. The background is the solid vertical backdrop against which the remaining decor is displayed, i.e. it should represent the actual bank or vertical reef.

It is unkind to keep fish with bare glass on all four sides, unless the tank is large enough (unlikely in domestic aquaria) to build a central mass of rock, effectively a four-sided internal backdrop to the surrounding activity. For this reason we do not approve of the use of tanks as room dividers with the two long sides both used as viewing panels. It is possible to buy plastic pictorial backgrounds showing roots and plants, rocks or corals. Alternatively the outside of the back of the tank can be painted, preferably a dark, bank-like color for freshwater and brackish aquaria. Plain black is very effective, and for something less permanent than paint, use black polythene. Other possible external backgrounds include cork tiles or dark carpet, internal ones include pieces of slate. Because lava or tufa rock are relatively porous and lightweight, they are sometimes piled at the back of the marine aquarium to create a realistic representation of a reef wall.

Any internal background must be nontoxic, as must paints, varnishes or glues used.