There are many reasons aquarium or pond water can become clouded. A few of these may be due to gravel vacuuming, or perhaps the fish have just spawned which can cause a temporary light cloud in the water. These conditions are normal and if filtration is adequate the cloud will be gone within a short time, but when a cloud comes and doesn't go away; this means the water isn't being filtered properly and the pump isn't delivering enough of the right kind of action.
White clouds are caused by bad bacteria free floating in the water; we call this a bacteria bloom as seen in the photo.
Yellowish or greenish colored clouds are caused by algae
forming in a new set up. We call this an algae bloom. Algae forms as the
nitrogen cycle completes and nitrate levels climb, and often starts off as a
cloud. If there's not enough oxygen in the water (surface action) the algae will
continue to float freely in the water; deepening in color and consistency; we
call this green water algae.
If your tank or pond water is heavily oxygenated; in order to survive, the algae will be forced to grow on substrate such as gravel, tank walls, decorations and pumps alike, but the water will be clear; we call this type of algae, substrate algae.
Waste is heavy and settles to the bottom of the tank in a short time if it's not trapped in a filter or sponge. This is why we use a gravel vacuum; to remove the waste that has settled in it. If there's little or no gravel, there's no place for the waste to settle, and it may easily be stirred up by fish searching for food, and this could cause a cloud in the water, but only if there's little or no filtration. These types of clouds are typically close to the same color as the food that the fish are being fed.
If your tank or pond is clouded, this indicates oxygen levels are low. You may see the fish at the surface gasping for air; not good.
If your tank or pond has a mixed gender; you may notice a bit of a cloud during or after a spawning session; along with a fresh fishy odor, but the cloud subsides in a short amount of time along with the smell.
Supersaturated gases are concentrated amounts of oxygen found in tap water. These tiny bubbles can float freely in the water causing a cloud, but they can also cling to the decorations; gravel; tank walls and even worse....your goldfish.
To discourage clouds; increase oxygen levels by increasing the action in your set up. If you have an aquarium, make sure the surface is exposed to fresh air by removing top. Make sure your pumps and filters have thick sponges and rinse them every time you perform a water change. No matter whether a cloud is caused from bacteria, algae, waste or gases in your tap; it will quickly be eliminated with the proper set up and maintenance.
Author: Brenda Rand