The effect of environment on health
To some it may sound a bit strange, but fish need to feel comfortable and safe in their surroundings if they are going to be healthy and experience a good quality of life. Any factors that cause stress are detrimental to health and will prevent fish from exhibiting normal healthy behaviour. Stress can prevent feeding, cause behavioural changes, and reduce immunity, allowing diseases to take hold. In the wild, one of the biggest stress factors to small fish, which includes the majority of aquarium species, is being preyed upon, so the fish goes to great lengths to avoid this. The relationship between a fish’s environment and its need to avoid being preyed upon is still present in the aquarium, even if there are no predators around. Looking at the common ways some fish use the environment to avoid being preyed upon reveals some interesting relationships, and highlights how the wrong environment can cause stress.
Substrate / Gravel
If you look at many aquarium fish, with the exception of selectively bred colour forms like platies, you will notice that a lot of fish have a lighter underside and are darker on top. In the wild this is a form of camouflage, predators looking down on the fish see the darker topside against the background of a dark substrate, whilst those looking from below see the lighter underside against the bright sunlit waters surface. If the substrate in a natural environment were a bright colour, like coloured gravel, the fish would be easier to spot by predators and might be quickly eaten. Putting some fish in an aquarium with bright gravel can cause them to feel exposed, more likely to be spotted by predators, and stressed. Most fish prefer a dark or natural coloured substrate.
Plants
Natural plants provide an obvious and recognisable hiding spot for fish, and can significantly reduce stress and improve colour and appearance of many aquarium fish. Artificial plants are better than nothing and will still provide hiding spaces, but stick to more natural looking artificial plants, a bright purple plant may not be an ideal hiding spot. Many fish also like to nibble at the leaves of real plants and they contribute to a richer diet so if possible, always have some real plants in the aquarium.
Shoals
When you try and buy two fish from your retailer only to be told they should be kept in groups of at least six, it is easy to think they are after a quick sale, but they are probably entirely correct and should indeed be making sure you get a group, or shoal, rather than a couple of individuals. In nature, one of the best strategies for avoiding being eaten by predators is to be part of a large group. Ten pairs of eyes can keep a much better lookout than two, a predator can find it difficult to focus on one individual target out of a group, and even if the predator catches one individual it is only a one in ten chance of being you. When shoaling fish, like many tetras or small barbs, are kept in small numbers, they are constantly on alert for predators and do not feel comfortable, causing stress and ill health. When kept in groups, even if they do not swim tightly together, a fish knows there are others of its type around, and feels much safer. Some fish even see the presence of other shoaling fish as an indication that the environment is safe to swim around. In these cases, fish that appear nervous and hide away can be brought out in the open by simply introducing a large shoal of small fish to the tank.
Natural wood
Both real bogwood and artificial wood provide good hiding spots, but some algae eating catfish actually need real wood to help aid their digestion. In these cases, the fish grazes on the surface layer of the wood and obtains enzymes which help to digest food, so in aquariums with algae eating, or sucker mouth catfish, there should always be at least a small amount of real bogwood.
Caves & hiding spots
Even if your fish do not appear to use the wood, plants, rocks, or other decorations in your tank, it is important that they are there. After a fish is established in a tank, it knows where most of the good hiding spots are, and simply knowing the route to a hiding spot is enough to give the fish an element of safety and confidence to swim out in the open. In the unlikely event of a predator appearing, the fish knows where to ‘run’ to, so it does not feel exposed. For the same reasons, it is best to use a dark background rather than a bright artificial looking scene. The dark background is a good place to hide, and the fish knows that nothing happens in that area (such as people walking by), making it a safe and secure area, which is always in reach.
Use a natural or dark coloured substrate, try to use at least some live plants and make sure there are some densely planted areas, keep shoaling fish in large numbers, use natural wood, and provide plenty of dark spots and hiding places, including a dark background. Follow these simple tips and along with good water conditions, filtration, and maintenance, your fish should thrive.
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