Gravel Coloration Issues in a Fish Tank
- A green slime that commonly covers aquarium gravel is the result of cyanobacteria. Commonly called blue-green algae, cyanobacteria are organisms that exhibit both plant and animal characteristics in their life cycle. The slimy blue-green blankets of cyanobacteria can mar the appearance of an aquarium as they cover everything from the gravel to plant leaves in a short amount of time. The slime can be removed by hand or by gravel cleaners, but the blankets of growth will return quickly if the underlying issue is not addressed. Usually, cyanobacteria proliferate due to excess organic matter in the tank, so keeping gravel clean and free from excess food is an important way to prevent the appearance of blue-green algae. If the cyanobacteria have a stronghold in your tank, you may have to treat it with an algaecide treatment or by covering the tank with a blanket to keep out light for three to four days to kill off all the algae. Once treated, you should vigorously attend to the tank, ensuring that the gravel remains clean and free from any organic matter so the cyanobacteria do not return.
- Red algae are one of the most frustrating to deal with in an aquarium, and can come in a variety of forms and colors. Red algae can form as a thread-like structures, cover the surface of rocks and attach to filtration devices and appear red, gray-green, or even purple. Most often, red coloration issues are a result of algae known as beard algae. Beard algae enters the aquarium through the introduction of a new plant or animal that brings small amounts of the beard algae with it. Once established in your tank, beard algae are difficult to remove. One of the best ways to control the growth of unwanted beard algae in your aquarium, once it is established, is by limiting nutrients. Iron is a trace element needed by all aquatic plants for healthy growth. By experimenting with the control of iron—adding enough to keep other plants healthy, but depriving the algae—in combination with manual removal of the algae from the gravel, you can slowly reduce the amount of beard algae in your aquarium.
- Soft-looking clumps of brown growth on aquarium gravel are not caused by algae, but by small creatures called diatoms. The brown growth usually occurs as a result of too little light or an excess of silicates in the water. They can be removed by siphoning the dark clumps up with a gravel cleaner or introducing algae-eating fish or snails. If the brown growth is persistent in your tank, try increasing the level of lighting. Diatoms are light-sensitive, and a strong light will help keep them for growing in your aquarium.