COUNTERING ALGAE PROBLEMS
Algae can be removed by hand, by sliding the leaves of the plant between the
thumb and index figure, by rolling filamentous algae around a stick, or, finally,
with a scraper equipped with a razor blade or a small scouring pad (available commercially,
although you can also make one yourself). Any rocks, sand, coral skeletons, branches,
or roots infested by algae can be treated, outside the aquarium, in a 10% bleach
solution, to which these algae are very sensitive. Any submerged equipment colonized
by algae (heating, pipes, diffuser, filter) can be treated in the same way. It is
important to rinse and dry them thoroughly before putting them back into the tank.
Sometimes, however, the proliferation of algae can be so extensive that the only
option is to create a whole new aquarium from scratch.
DIFFERENT GROUPS OF PROBLEMATIC ALGAE
Red algae (Rhodophyceae)
It is unusual to find a proliferation of these algae in an aquarium.
Brown algae (Pheophyceae)
In an aquarium, these mainly consist of diatoms, unicellular microscopic algae.
These grow and form a thin film on the decor and glass panes of the tank. Under
poor ecological conditions, they can follow from certain green algae.
Green algae (Chlorophyceae)
It is generally considered that their appearance in small, sparse clumps is a
good sign (especially in alkaline water) that may indicate that the aquarium is
well-equipped. However, if they proliferate they create two main types of problem:
- green filamentous algae; this is probably one of the types of overgrowth
most often seen. These algae are very thin and, although they sometimes only
grow to a few centimeters in length, they can extend to several dozen centimeters.
They reproduce through fragmentation, with one very short filament, invisible
to the naked eye, sufficient to colonize an aquarium in a fairly short space
of time, if the conditions are right;
- green water; this is caused by the widespread growth of microscopic algae,
generally unicellular, which can move around with the help of a flagellum. In
a natural setting, these constitute phytoplankton. They often proliferate rapidly
when the concentration of nutritional elements (mineral salts), particularly
nitrogen, is too high, in strong light.
Blue algae (Cyanophyceae)
Also microscopic, these are extremely ancient in origin: they were among the
first living elements to appear on Earth. Despite their name, they form a green-blue,
sometimes brownish, layer with a velvety sheen. They often develop if the lighting
A disposable razor is useful for eliminating algae that
grow on the aguarium panes.
Try to regulate the factor provoking the algae overgrowth by adjusting the amount
of light, which should be reduced in the case of green or blue algae. Changing the
position of the tubes, or the addition of deflectors, to keep algae off the front
of the tank, produces good results. In freshwater aquariums, you can make partial
water changes, on a fairly regular basis, using water with a low hardness containing
few mineral salts.
Be careful, however, not to make any drastic alterations to the quality of the
water if this has been specially adjusted to specific plants and fishes.
In seawater tanks, change the water, replacing it with reconstituted water of
the same salinity.
These can involve the use of herbivorous animals only interested in certain types
of algae, such as the fish mentioned above or gastropods (rare in sea water).
The battle on the biological front is sometimes fought without any intervention
on the part of the aquarist, as larger aquatic plants release substances that can
inhibit the development of algae.
The extent of this phenomenon is very difficult to appreciate in an aquarium,
as it is invisible to the human eye.
Several fish can be used in the biological battle against
algae in fresh water: Epalzeorhynchus siamensis (right) and Gyrinocheilus aymonieri
There are special products on the market designed to kill algae. As their effect
has not been fully established, it is best to be cautious with the dosage, as these
substances probably also affect other plants. For the same reasons, the use of copper
sulfate is not recommended, as it is dangerous for invertebrates.
There is no miracle solution. The use of several techniques at the same time
sometimes has positive results, but it is not unusual to find that the algae reappear
after a while. It is best to get used to partially eliminating them on a regular