A brown algae forms in the immature aquarium, gradually replaced by green algae as
the water matures. It is best removed mechanically - use a plastic pan scourer
and prevent reforming by adding an algae-magnet (any aquarium shop sell these). Or
ignore and wait for it to turn green - then some fish will eat it (they do not like
the brown).
All algae, whether red, blue-green, brown or black, photosynthesises so turning off
the lights will cause algae to fade away (remember to remove dead and dying algae
or it will pollute the water). Plastic plants are needed of course, any real plants
should be moved to another tank.
An alternative is to use coloured lights (since photosynthesis requires white - i.e.
full spectrum - light). The simplest way to do this is to place a layer (or two)
of red or green (or both at different ends of the tank for a pretty effect) cellophane.
The cellophane can be safely wrapped around fluorescent tubes (but not filament
bulbs - too hot). The material can be bought from Art Shops and some Florists.
Over marine tanks fit coloured dichroic spot lights, one red, one green (orange and
yellow looks good too, blue is usually too dull) shining through a glass top. The
bleached coral remains white for many months and the air bubbles of the pump pick
up the colours giving a pretty scene.
Another idea in freshwater tanks is to use water soaked over hay because there is
some extract, not yet identified, that suppresses algal growth without harming the
fish. The Koi keepers use this system routinely and Lily growers always add a sprig
of hay to the growing ponds. Worth a try if coloured lights are not possible.
The best fish for eating algae in the tropical aquarium are Bristle-nose Catfish
such as any Ancistrus spp, Sucking Loaches, such as the Chinese Algae Eater Gyrinocheilus
aymonieri, Siamese Flying Fox Crossocheilus siamensis or a Plecostomus (but only
in large aquaria because the fish grow large too). Many of the Live-bearing Toothcarps
such as Mollies, Platies and Limias will browse on algae e.g., Poecilia sphenops
or velifera, Xiphophorus maculates and Limia melanogaster but algae can outgrow the
small amount they remove.
Another method is to fill the tank with well-growing aquatic plants so the algae
cannot compete...for best growth the roots need to be in loam (not peat - use loam
for nutrients) in minipots. If not possible, use a sandy base rather than gravel.
Add floaters too.
Phosphates will encourage algae - you can test for the level with a phosphate kit
and if present, use a phosphate-remover such as API’s Phos-Zorb (all good aquashops).
Yet another idea is to check the pH, Greens and Blue-greens usually grow in alkaline,
hard water, so alter the aquarium chemistry (slowly) with rainwater soaked over peat
for acidity and softness. You do not see algae in the upper Amazon...
