For most aquarium decorations, remove loose algae with a clean toothbrush, soft brush or aquarium-safe pad. Avoid soap, detergents and household cleaners. If the item is porous, painted or delicate, follow the manufacturer's care guidance and avoid aggressive soaking chemicals. Clean only as much as needed; algae on hardscape is not automatically harmful.
Decorations attract algae because they sit under the same light and nutrient conditions as the rest of the tank. The simplest solution is usually physical removal rather than trying to sterilise every surface.
Start with mechanical cleaning
A toothbrush reaches grooves and corners well. For broad smooth surfaces, use an aquarium-safe pad.
Work over a bucket or sink reserved for aquarium items and keep soap away from the equipment.
Know the material before soaking
Ceramic, resin, painted ornaments, natural wood and porous rock react differently to cleaners. When in doubt, use plain water and brushing rather than an aggressive chemical treatment.
Do not chase a sterile look
A thin film of algae or biofilm is common in mature aquariums and can be grazed by fish, shrimp and snails. Remove it when it is unsightly, trapping debris or affecting the intended use of the decoration.
Fix the reason algae returns
- Reduce excessive lighting duration or intensity.
- Remove excess food and detritus.
- Maintain consistent water changes.
- Support healthy plant growth where appropriate.
- Avoid placing the tank in strong direct sunlight.
Rinse before returning decor
After cleaning, rinse thoroughly with aquarium-safe water so loose debris is not dumped back into the tank. Reposition items carefully so they remain stable and do not trap fish.
Related aquarium tools and guides
Frequently asked questions
Can I use bleach on aquarium decorations?
Only with materials known to tolerate it and with complete neutralisation afterwards; for routine cleaning, brushing and rinsing are safer.
Can I use dish soap?
No. Soap residues can be harmful to aquatic life.
Is algae on decorations harmful?
Usually not by itself. Heavy growth can be unsightly and may indicate excess light or nutrients.
Sources and further reading
This guide separates general aquarium arithmetic from fish-welfare decisions. For species-specific limits, always check the needs of the fish you intend to keep.