from the blog

The Slime Coat: What it Does and How to Protect it

Care and maintenance

September 30, 2020

The body of every fish is completely covered by a mucus layer known as the slime coat. A fish's first - and best - defense against disease and parasites lies in the slime coat; it acts much like a human's top layer of skin by keeping out harmful substances and regulating the fluids within the body. The problem is, this slime coat gets damaged very easily and many beginning aquarists have no idea how crucial it is to keeping fish healthy. While this coating can be somewhat protected and replenished by products that contain aloe, simple treatments will never be enough if you do not take care of the underlying cause of the damage.

The first major cause of damage is simple mechanical damage. Whenever you net a fish, or a fish gets it in its head to attack another fish or it brushes past an artificial plant, that is when the slime coat gets damaged. Often it is only minor scrapes that can heal easily provided no other slime coat hazards are present.

The second major cause is stress. This can be stress from moving, from water changes, or the worst kind...the stress of living in inappropriate water conditions. Make sure your temperature does not vary widely throughout the days and nights; ideally there will be no more fluctuation than about two degrees Fahrenheit. Ensure that your tank is well-aerated; as long as the water surface is moving you have oxygen exchange, but if the fish are often seen at the top "gasping" for air you will need to find a way to further aerate the aquarium.

Of all the inappropriate water conditions, an improperly cycled tank is the most deadly. Coming in second place - an aquarium in which too many fish were added at once. The result: ammonia in the water. Ammonia is the extremely toxic by-product of fish waste and decaying uneaten food, and even at trace levels it will swiftly dissolve the slime coat and kill the fish. To avoid this, be sure to allow a full 36-day cycle to be completed before you add fish, use filter media or a handful of gravel from an established tank, or use a commercial product such as EcoBio-Block that will introduce the necessary beneficial bacteria to the aquarium.

Do regular partial water changes to keep nitrate levels down and remove waste and other organic material, as well as replenish essential minerals in the water that the fish need to survive. If you do not have the time or physical ability to do 2-4 water changes per month, a combination of a strong mechanical filter and an EcoBio-Block can significantly cut down the number of water changes needed. The EcoBio-Block leaches the necessary minerals into the water for up to two years in addition to adding in the beneficial bacteria, so be sure to keep it in the tank if you have one!

As long as you keep your water parameters within healthy limits, handle your fish with care (make sure to soak your nets before using them, dry fibers are much more damaging) and add an aloe-containing product to the aquarium after stressful events or whenever a fish is sick, your aquatic critters should keep a beautiful, healthy slime coat that will greatly reduce their risk of disease and parasites.

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