Brown algae a common problem for new tanks
What is brown algae?
Brown algae is a form of algae called diatoms that can photosynthesise as well as eating chemicals in the water. So they can survive even in low light levels as long as their alternative food sources are available. Silicate, phosphorus and nitrates in the water are potential food sources for them.
Recognising brown algae.
When you see a light to dark brown blotches which appear as a slimy film covering any aquarium surface then you are highly likely to have brown algae. It is easily displaced from any surface and can be vaccuumed off glass, plants and gravel.
What causes brown algae?
It usually comes about when there is low light levels, low green algae or plant growth and when there is an abundance of silicate, nitrate or phosphorus in the aquarium. This usually happens in a new aquarium. The silicate can come from the glass of a new aquarium leaching silicate into the water or from newly used sand leaching silicate. Sometimes the rocks in the aquarium contain minerals that feed brown algae so may need removing.
Is brown algae harmful?
It can be harmful to plants or corals because it can coat them and block sunlight and nutrients to them. It the algae starts to die it can cause pollution problems. However, many algae eating fish will relish brown algae and is generally not harmful if it doesn’t overly cover plants or corals.
How can you cure brown algae?
The best way is to deprive the algae of the nutrients that the it feeds off. Correct the lighting problem, such as buying a new light if your aquarium bulb is old or buy a brighter light. The algae will take up the nutrients from the newly set up tank. Once the tank has matured the algae should run out of food.
The second way to cure brown algae is to continually scrape it and syphon it from the aquarium. The nutrients locked inside the brown algae will also be removed along with it. When you scrape off the algae make sure it is removed from the water. If it is allowed to remain in the water it will simply re-attach elsewhere or it might die and leave silicate in the aquarium water, so will re-appear. If the water you are using contains silicates and phosphorous then you might either need to put silicate/phosphorus remover in your aquarium or you could try mixing tap water with reverse osmosis water.
Removing any suspect rocks or gravel in the aquarium and replacing with safer gravels without silicates or phosphorus. Sometimes all it takes is to wait for the aquarium to cycle and mature. The brown algae usually gets overtaken by green algae.
Add a couple of otocinclus catfish which will devour it. In a saltwater tank fish like yellow tangs like to eat it too.
I suggest you avoid any chemical treatments to kill off the brown algae because of the side effects on your other tank inhabitants and the harmful effect on the biological filter.
Preventing brown algae.
Use good lighting. Set up fast growing plants. Use safe gravel or aged sand. Check out the mineral content of your rocks. Do not overfeed the fish. Make sure you cycle your aquarium properly. Use a silicate free source of water such as reverse osmosis water.
Brown algae in a saltwater tank
Check for silicates in your saltwater mix. Look through the list of ingredients to see if any silica based compound is in the list. Try using reverse osmosis water rather than tap water for your saltwater mix. Make sure you clean the brown algae off the corals daily. Use a phosphate/silicate-absorbing material in the filter.