Laying the Groundwork

Retailers should brush up on their substrate knowledge to effectively sell the category to both new tank owners and hobbyists looking to replace old gravel.


No aquarium is complete without substrate on the tank floor. Every tank sold requires some form of material on the bottom. This may be shallow or deep, depending on the owners’ tastes, but the need for this substrate is irrefutable. Likewise, the necessity to replace this material every few years is equally unchallenged­—a change makes the tank owner and the aquatic inhabitants happier. Whether a retailer is selling substrate to a new tank owner or to someone who is changing their gravel, these sales can help boost a retailer’s bottom line. All it requires is some creative advertising and merchandising, as well as the right product inventory.

Freshwater Substrates
Freshwater substrates come in a variety of colors and grain sizes. Colored gravels are coated with a layer of waterproof paint, and natural gravels may be covered with a clear layer of plastic. Both types of gravel are coated to prevent the gravel from coming into physical contact with the water and creating a chemical reaction between the minerals in the substrate and the water. Since many minerals are water soluble, this is a good thing. Inert or coated gravel is the right choice in most freshwater environments.

There is a rainbow of colored gravels to choose from, but most products comes in a single color. A few gravels are bi-colored (grains of two different colors), and every company produces at least one multi-colored gravel, as well. Grain size is usually a “No. 2;” anything larger is called pebble gravel.

The most common type of gravel sold is undoubtedly “natural,” which means it is not painted or dyed--but it may still be coated in clear plastic. Still, natural gravel is multi-colored, since it contains natural rocks of different hues. Very few natural gravels are uncoated, and these produce some vivid hues underwater. Before stocking these, try to ascertain their suitability as far as chemical activity is concerned.

Gravel color is important to fish, maybe even more important than it is to people. Most fish in a freshwater habitat seem to prefer a dark or natural gravel, while marine, brackish-water and Rift Lake species are used to white sand or gravel. Keep in mind that many fish will not color up properly if the substrate clashes with their body colors.

Many fish are cave dwellers or “lurkers” that shun the reflection given off from a light substrate. Neutral gravel is good for tanks that house a community of fish exhibiting many different colors, shapes and sizes. Retailers should consider offering this basic gravel at a slight discount, since they are going to sell a lot of it. This is also the gravel to include in complete tank kits.

Gravel comes in bags of various sizes, ranging from five lbs. to 40 lbs. Most companies avoid selling anything heavier than 40 lbs. for obvious reasons. No matter the bag weight, however, gravel is one product retailers stock at or near floor level. This means, to attract attention to these products, retailers must use signage. Retailers can use point-of-purchase materials, but even more important are remote ads that remind people to check out the “substrate” aisle. Consider positioning placards near the front entrance, as well as at several locations throughout the freshwater livestock department, and include information about gravel type, color and grain size. For example, spiny eels, freshwater stingrays and many loaches love to burrow in the substrate, so their tanks are best outfitted with fine sand-like gravel.

Storeowners should generally avoid displaying a variety of gravels throughout their freshwater livestock sections, since it makes the placement of fish difficult if you have to take into consideration different gravel colors and/or different background colors. Instead, pick out a natural gravel for most tanks, and a light-blue color for the background. Specialty fish can have their dedicated environments since these will rarely vary, but keep the majority of aquariums looking identical so you can move fish from one tank to another. If you want to showcase a gravel product, you can do so in a “display” tank in which the fish are not for sale.

Planted Aquariums
The makeup of substrates for planted aquariums differs greatly than those for tanks where plants are not the main focus. These “aquatic garden” substrates are useless in tanks without live plants, because they are designed specifically for that purpose. Many aquatic plants will grow quite well in regular gravel, others will not. Retailers should convince customers who are serious about their planted tanks to use plant substrate. The true value of using this product can only be conveyed in a display tank that showcases a variety of plants.

There are numerous gravels marketed for African Rift Lake cichlids environments, and they are truly diverse in chemical properties, grain size and grain color. Unless they are displayed in tanks, people are unlikely to purchase them. In general, I prefer gravels of an intermediate grain size—not too small, not too large. Darker gravels in rift lake tanks tend to affect the color of the fish­—the fish expand their chromatophores and darken up more than I think they should. Still, it comes down to a matter of personal preference. And, dark gravels are great for many substrate spawning Tanganyika species, which like to be hidden.

Marine Substrates
Marine substrates come in both “live” and “regular” forms. Live gravels are meant to contain a large number of trace elements found in natural seawater, as well as live bacteria, which help seed tanks for driving the nitrogen cycle. This means these bags of gravel have liquid in them and have a definite shelf life. You must be careful not to tear the bags when handling these products. You must also cycle the bags carefully, so it does not go out of date. The main drawback with live sand is that it clouds the aquarium, sometimes for several days. If you are setting up a tank, you must have all rock in place before adding water. Live bacteria from a bottle can accomplish the same thing without clouding a tank as much.

The gravel debate rages over the use of sand/gravel in reef tanks and some people still choose to go sans gravel. Fish, however, prefer a substrate, and there is nowhere in the world where coral does not live over a substrate. It may not live directly on the gravel, but the gravel is there. Substrate is also important to the aesthetics of a tank. Otherwise, it looks like a factory with equipment, bells, whistles, bright lights, and no soul.

Edward C. Taylor has been in the pet industry for over 30 years as a retailer, live fish importer and wholesaler, and fish-hatchery manager.

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