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Forming slimy green growths on aquarium rocks, decorations and walls, algae are actually a sign that your tank is functioning normally. Algae feed off dissolved nutrients from fish waste, uneaten food and rotting plant debris. Providing there are nutrients in the water and sufficient light, algae grow continually, so regular removal is necessary. Washing decorative rocks under running water removes most algae, though some additional scrubbing may be necessary for long-term growth.
A Wash and Brush Up
Checking aquarium rocks and removing algal growth is part of regular tank maintenance. Clean and check aquarium rocks every three or four weeks. Remove them carefully from the tank to avoid stirring up sediment, hold them under cool, running tap water and rub off any algae. A soft-bristled brush, such as an old soft toothbrush, helps remove stubborn growth. Check the rocks for sharp or rough edges, which can injure fish. Either file away the edges or dispose of the rocks. Crumbling and flaking rocks turn tank water cloudy, so remove those, too.
Live rocks in saltwater aquariums require special care. Live rocks contain living bacteria that perform an essential role in keeping saltwater clean. Wash live rocks in saltwater to preserve the bacterial population. Scrubbing them gently with a brush isn't harmful.
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