General Notes on Algae
by Joe Schill
First published in Tank Talk, Canberra and District Aquarium Society, Australia
Algae are always present in a tank at least in dormant form, and a small quantity
growing here and there is to be taken as a healthy sign. However, the trouble starts when
growth is excessive. To counter this it is essential first to find out what pertaining
conditions are favouring the bloom.
A most likely primary cause would be that the tank is over-stocked with fish, giving
rise to unduly eutrophic (nutrient rich) water. To some extent this may be countered by
the presence of plenty of actively growing higher plants but there are very definite
limits to this strategy alone.
Another important factor is lighting and an aquarium should never be located near a
window, where it will receive too much sunlight (only a maximum of 2 hours is
By World standards, Canberra tap-water is very soft and this also favours algal growth.
In general, a GH of 6 or higher is to be recommended, although certain special fish, such
as Discus and some South American Tetras, require softer water.
Some snails will eat algae but they are seldom able to control it effectively. The same
can be said of certain fish, such as Gyrinochellus and some Malawi cichlids,
which cannot be kept together in a tank in sufficient numbers. However, the Bristlenose
Catfish, Ancistrus temmincki, is perhaps a notable exception. Such fish (and
also, many cyprinidae) actually need algae as part of their diet and the maintenance of
suitable levels of growth, without allowing the algae to take over their tank, calls for
some nice judgment of stocking levels and water quality management.
Other points to be noted are:-
1) A fast flowing filter will help to control algal growth, which is always diminished
in turbulent waters.
2) An algal bloom nearly always occurs in a new tank but this will normally subside as
a state of maturity is reached.
3) Sometimes a golden film will appear on the water surface but don't worry: this will
4) Algal growth is seasonal.
5) Green algae grow if there is too much light; brown algae grow in under-lighted
conditions; blue-green algae generally indicate problems of water chemistry.
6) Never use garden soil for aquarium plants in a tank or ornamental pool as this will
provide a starter for algal growth.
7) Dense algal growth in an aquarium, if not controlled, will eventually kill off most
of the other plants.
8) Most algicides also harm other plants and fish in a tank.
9) Covering a tank with a dark cloth for a week will kill off algal growths but the
other plant and fish life will survive the treatment.
10) Every tank has its own special conditions and there is thus no standard cure-all
treatment; therefore try to solve its problems through a blend of useful tips acquired
from others and from personal experience.