Algae: Description and Control in Freshwater Aquaria
by Andrea Watts Reprinted from www.sydneycichlid.com
What are algae?
Most people will agree that algae are an unattractive and unwelcome addition to an
aquarium especially a planted biotope. It can hinder plant respiration and
photosynthesis (hence affecting growth) by smothering the leaves of green plants. Rampant
algae growth is particularly relevant in newly setup aquariums. They readily establish in
new tanks in a similar fashion to weeds colonising freshly cleared or turned over soil.
When an aquarium is first set up with fresh water and new plants, it takes time for the
latter to adapt to their new conditions, put out roots and start to grow. Algae adapt far
more quickly and an algal bloom occurs as they feed on the nutrients in the fresh water.
At this stage the reaction of most people is to change the water and start all over again.
This will only aggravate matters, as the new water will once again feed the algae. It is
far better to allow nature to take its course and the tank to progress through the natural
cycles. Achieving a fully planted aquarium with healthy fish and plants takes time
months, in fact.
Many will be familiar with algae in the form of green or brown encrustations on the
rocks and glass in aquaria (e.g. beard algae), as greenwater (single-called free-floating
types) or as thin, tough green filaments (e.g. hair algae) which can prove extremely
difficult to eradicate. It often comes as a surprise, therefore, to learn that some algae
can actually cause diseases in fish.
Like plants, all species of algae need light, water and nutrients to grow. It is up to
the aquarist to limit the amount of light and nutrients received by the aquarium in order
to keep algae in check. The three main nutrients that algae need are nitrogen, phosphorus
and potassium. In an aquarium, these nutrients come from fish waste, uneaten food, the
metabolism of beneficial bacteria, and the decay of other organics (e.g. plant debris and
even dead algae). Some regions have trace amounts of phosphorus in the tap water. You can
reduce the accumulation of nitrogen through water changes; phosphates can be kept in check
using phosphate-removal media (e.g. phos-rid) in an external filter or by using reverse
osmosis water for the aquarium.
Types of Algae.
Greenwater: Caused almost invariably by too much light. The name aptly
describes its appearance tank takes on the pea soup look. Filtering
with micron cartridges or diatom filters will successfully remove these algal blooms.
Greenwater is a great source of nutrients (food) for species such as brine shrimp, Daphnia
spp. and minute fry and is often purposely cultivated for this purpose.
Brown encrustations (slimy appearance and feel) on plants, décor and
glass: Often accompanied by poor plant growth. It is an indicator of insufficient
illumination. It is easily removed by wiping the surface.
Above photos - brown encrustations
Green encrustations: Two types: fuzzy and beard. The fuzzy
algae is not of great concern and can be controlled via the addition of grazing fish. It
is easily differentiated from beard alga in appearance. It grows in short, single strands
of about 2-3mm. Beard algae is more serious. Its individual strands have a very fine
texture. It grows in thick, furry patches, up to 4cm. Its resemblance to a green beard
gives rise to the name. It cannot be removed mechanically.
Above photos - "fuzzy" or
Spot algae: The small round green spots that appear on the sides of
the aquarium are not algae. These are actually populations of diatoms, microscopic animals
that secrete a hard silica shell on which green alga grows. This type of algae
is the most difficult to remove. A sharp blade works well.
Filamentous algae: Two main types: hair and thread. Hair algae have
shorter strands than thread algae (around 5cm in length) and tends to form matted clumps.
Thread algae have much longer strands (as long as 30cm) and is often an indicator of
excess iron. Both are quite easily removed with a toothbrush.
Above photos - forms of hair algae
Staghorn algae: As the name suggests, this branching alga looks like
miniature greyish-green stag antlers. It is mostly seen nearer the tank surface,
establishing itself on filters and décor. It is very difficult to remove mechanically and
most aquarists resort to chemical control.
Brush algae: Brush alga is blackish (actually classed as a red algae)
in appearance and forms feathery tufts about 2-3mm long. It is a nuisance on décor,
filters and broad leaf plants especially. Being extremely difficult to remove, chemical
additives seem to be the only way to rid aquariums of this menace. True SAE have been
found to be somewhat effective in its control.
Above photos - brush algae
A type of branched alga.
Controlling Algae in the Aquarium.
Following is a list of some suggestions for alga control in your aquarium.
1. Dense planting. Planting your aquarium densely from the onset will
help to deter the establishment of algae. Rapidly growing bunch plants (plants
that are grown from cuttings and sold in bunches at the LFS) fall into this category. They
will utilise the nutrients in the aquarium very quickly, making it difficult for algae to
2. Water changes. Regular, large water changes help to eliminate the
nitrogenous waste and phosphates that algae need to thrive. Replace half the water every
week (or at least every second week).
3. Introduce algae eating fish. There are many suitable species that
can be introduced into the aquarium to help control algae. They should be added sooner,
rather than later. Do not allow an alga problem to develop before adding the fish. Most
fish will not be able to eat enough algae in an all ready overgrown aquarium. If they are
sparingly fed, they will be forced to look towards the algae as a food source. Suitable
additions include: Otocinclus spp. dwarf plecos, whiptail catfish, and members of the
Loricariidae genus and most live bearers (e.g. Mollies). Large plecos are not suitable, as
they tend to munch on plants and outgrow the tank. Members of the Corydoras spp. help to
stir up the substrate and help deter algae from settling and taking hold.
4. Light starvation. Decreasing the amount of penetrating light that
an aquarium receives can sometimes control algae. This action may be as simple as reducing
the amount of time that the lights are in use or positioning the tank so that direct
sunlight is limited. Blackwater extracts or wood (tannins) can help to darken the water
and starve algae of the light needed for photosynthesis. Floating plants may help, however
they will also reduce the amount of light that penetrates down to your plants.
5. Physical removal. Filamentous algae can be reduced by gently
combing and winding the strands around a small brush (e.g. toothbrush). Ornaments/décor
can be lifted from the tank and brushed or soaked in bleach or potassium permanganate.
Remember to thoroughly rinse the décor to rid it of residual chemicals before returning
it to the aquarium. Algae scrubbers are a cheap investment from the LFS.
6. Chemical control. A product called Health Guard (from Seachem) is
excellent for controlling all algae, including blue-green algae. It is safe for all plants
and fish. When all else fails, the addition of copper sulphate can be considered. A weak
solution of copper sulphate (bringing the copper concentration up to around 0.3-0.5ppm)
will kill algae but may kill some aquarium plants too. It must be measured exactly
overdosing will result in plant and fish deaths. This is truly an act of desperation and
should not be considered lightly! When dosing is completed, be sure to replace the water
and use activated charcoal in your filter to remove traces of copper.
7. Ultraviolet sterilisers. These lights are set up after the filter
unit so that all water passes within a specific distance to kill any microscopic plant or
animal life within the water. They are very expensive units to buy.
8. Other methods of control. Some others methods of algal control
include: ozonization, reverse osmosis and resin exchange filters. Bottled or distilled
water for water changes can help exclude the addition of tap water contaminants.
Extra Notes. Some methods of algae control also present a
clean-up problem. If the dead algae collect on the substrate as sediment, the
cycle of decomposing organic matter produces more nutrients for more algae. The addition
of a coagulant or flocculent assists in the collection of this dying matter by causing the
single-celled plant forms to clump together. They can then be netted with a fine skimmer
net, vacuumed or filtered.
Dont overfeed your aquarium. If a fish dies, remove it immediately. Both
overfeeding and decaying fish add to the nutrient load in your aquarium.
Remember: Prevention is better than cure!