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  • How to Bleach Algae

    How-to Get Rid of Algae Instantly

    Author:  Jennifer Hamlin

    First Published in Aquarium World August 2013

    While this may sound like a ‘magic pill’ for everybody’s worst aquarium nemesis, it really is not. Algae grows whenever there are available nutrients and light so solving the cause of the problem is a more complex issue, however, it is possible to quickly improve the appearance of plants and fixtures in the aquarium with a simple treatment.

    The treatment for quickly eliminating algae on plants and surfaces involves chlorine bleach (sodium hypochlorite) which is poisonous to aquatic life. Bleach must never be used in a living aquarium, or anywhere near living fish.

    Bleach can be used on plants, fixtures, ornaments, rocks, and wood which have been safely removed from the tank. Once treated these can be rinsed well and safely returned to the living tank with no ill effects to the fish or bacterial filtration.

    To carry out this treatment, carefully follow the instructions below:

              Get some bleach – Chose a quality plain bleach solution. You get what you pay for. Cheaper brands often have much lower concentrations so they may not be as effective. Bleach also ages with time and the chlorine diffuses out of the liquid so an old bottle on the shelf will no longer have the same effectiveness of a freshly produced bottle.

           Prepare yourself and the environment – Concentrated bleach will discolour and eat away fabrics like clothing, carpet and furnishings as well as erode some metals. Prevent damage by preparing the solution in an environment that can handle some splashes if they occur. Wear white clothes, or clothes that you don’t mind getting damaged and wear gloves. Open a window for ventilation if the smell bothers you.

           Measure out 20mls (4 teaspoons) of bleach and add to a plastic bucket filled with about 1 litre of lukewarm or cool water. The amount is not exact and depends on the quality of the bleach. The more concentrated bleach you use, the faster it will kill the algae, however, if you use too much (e.g. more than 20%) it will risk damaging porous ornaments and fixtures and will certainly damage living plants. Take care and only use the minimum amount needed to do the job.

     Choose the fixtures, ornaments, and plants that you wish to treat and remove them from the tank. Rinse off any organic matter like mulm, fish food or rotting plants.

    Place the items into the bucket of diluted bleach and make sure they are submerged under the surface of the solution. Leave them in the solution for the time suggested in the chart below.

    Once the allotted time has passed, remove the items from the bucket and rinse well under a running tap. The solution will quickly rinse off but if you are worried, you can additionally submerge them in a bucket of water with added de-chlorinator which will neutralise any remaining bleach.

    The items can now be safely added back to the tank!


    Recommended exposure times of bleach-solution to get rid of algae on surfaces

    Ornaments & fixtures:

    Wood, rocks, plastic aquarium ornaments - up to 5 minutes

    Filter pipes, glasswear – up to 5 minutes

    Rubber fittings, sponges – up to 2 minutes

    Plastic plants – up to 5 minutes

    Silk plants  - not recommended


    Aquatic plants (living):*

    Anubias species – up to 5 minutes

    Cryptocoryne – up to 3 minutes

    Echinodorous – up to 3 minutes

    Rotala sp.– up to 2 minutes

    Ludwigia – up to 2 minutes

    Tiger lotus – up to 2 minutes

    All mosses – not recommended

    Bolbitis sp.  – not recommended

    Twisted Valisinaria – not recommended

    Indian fern – not recommended

    *Living plants that have damaged leaves will not hold up well to bleach so it is best to remove these leaves beforehand, minimize the bleaching time, or avoid bleaching the damaged leaves altogether. Many other plants can be bleached, if only for a minute or less which will kill the single-cells of the algae. Fragile soft-leafed plants are less tolerant of bleach so take care if trying this treatment on them.

    If the bleach solution is particularly concentrated, algae can immediately turn white. Some species of algae will turn pink or brown within minutes to hours after bleaching and some alage will just disintegrate once the ornament is placed back into the tank.   In a day or so, all evidence of the alage will be completely gone!


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