Algae : contributed by George Booth
The following descriptions and control techniques are for
common types of algae found in freshwater aquaria.
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There are two categories of algae of concern to aquarists: "good" and "bad".
Good algae is present in small quantities, is indicative of good water quality
and is easily kept in check by algae eating fish or simple removal during
routine maintenance. This algae is a natural consequence of having a container
of water with nutrients and a light source. Bad algae is either an indicator
of bad water quality or is a type of algae that tends to overtake the tank
and ruin the aesthetics the aquarist is trying to achieve. The label of
"bad" is entirely subjective. For example, one type of green, hair-like
algae is considered a plague by some American aquarists, yet is cultivated
by European aquarists as a valuable addition to most tanks, serving as a
dietary supplement for the fish.
Blue-green, slime or smear algae:
Grows rapidly in blue-green, slimy sheets. Spreads rapidly over almost everything
and usually indicates poor water quality. However, blue-green algae can
fix nitrogen and may be seen in aquariums with extremely low nitrates. Sometimes
seen in small quantities between the substrate and aquarium sides. Will
smother and kill plants. This is actually cyanobacteria. It can be physically
removed, but this is not a viable long term solution as the aquarium conditions
are still favorable for it and it will return quickly. Treatment with 200
mg of erythromycin phosphate per 10 gallons of water will usually eliminate
blue-green algae but some experts feel it may also have adverse effects
on the biological filter bed. If erythromycin is used for treatment, ammonia
and nitrite levels should be carefully monitored.
Forms in soft brown clumpy patches. In the freshwater aquarium, these are
usually diatoms. Usually indicates a lack of light or an excess of silicates.
Increased light levels will usually make it disappear. Easily removed by
wiping the glass or siphon vacuuming the affected area.
Green unicellular algae will sometimes reproduce so rapidly that the water
will turn green. This is commonly called an "algae bloom" and is usually
caused by too much light like direct sunlight. An algae bloom can be removed
by filtering with micron cartridges or diatom filters. UV sterilizers can
prevent the bloom in the first place. Green water is very useful in the
raising of daphnia and brine shrimp. Film algae Grows on the aquarium glass
and forms a thin haze. Easily removed by wiping the glass. Considered normal
with the higher light levels needed for good plant growth.
Grows in thin, hard, circular, bright green spots, usually on the aquarium
glass but also on plants under high light conditions. Considered normal
for planted tanks. Must be mechanically removed. On acrylic aquariums, use
a cloth pad or a gentle scouring pad like a cosmetic "Buff-Puff" and a lot
of elbow grease. On glass tanks, scraping with a razor blade is most effective.
<a href="http://www.aquaticscape.com/articles/algae/spot.jpg" target="_blank">
Grows mostly on plant leaves as separate, short (2-3mm) strands. Considered
normal. It might be a less "virulent" form of "beard" algae. Easily controlled
with algae eaters such as black mollies, Otocinclus, Peckoltia and siamese
Grows on plant leaves and is bright green. Individual strands have a very
fine texture but it grows in thick patches and looks just like a green beard.
It grows up to 4 cm. It cannot be removed mechanically. This does not indicate
bad water quality but grows very fast and overtakes the tank, making it
a "bad" alga. Can be eliminated with Simazine (Aquarium Pharmaceuticals
Grows in bright green clumps in the gravel, around the base of plants like
Echinodorus and around mechanical objects. It has a coarser texture than
"beard algae". Beard algae will ripple in the water current, hair algae
tends to form matted clumps. Individual strands can get to 5 cm or more.
This is easy to remove mechanically by twirling a toothbrush in it. Can
be troublesome if left unchecked. This is a popular food supplement for
fish among European aquarists.
Grows in long, thin strands up to 30 cm or more. Tends toward a dull green
color (hard to tell because it is so thin). Usually indicates an excess
of iron (> 0.15 ppm). Easily removed with a toothbrush like hair algae.
Looks like individual strands of hair algae but tends to grow in single
branching strands like a deer antler and is grey-green. Seems to grow mostly
on tank equipment near the surface. Difficult to remove mechanically. Soak
affected equipment in a 25% solution of household bleach and water to remove
This grows in feathery black tufts 2-3 mm long and tends to collect on
slower growing leaves like Anubias, some Echinodorus and other wide leaf
plants. Also tends to collect on mechanical equipment. This is actually
a red alga in the genus Audouinella (other names: Acrochaetium, Rhodochorton,
Chantransia). It cannot easily be removed mechanically. Remove and discard
the affected leaves. Equipment can be soaked in a 25% bleach solution,
then scrubbed to remove the dead algae. Siamese Algae Eaters (Crossocheilus
siamensis) are known to eat this algae and can keep it in check. A more
drastic measure is treatment with copper.
A really good article on this algae by Neil Frank
can be found at http://www.thekrib.com/Plants/Algae/red-algae.html
Prophylactics for Algae
Algal spores are everywhere and will always be present in an aquarium unless
drastic measures are taken. For fish only tanks, a properly set up ultraviolet
sterilizer will kill algal spores in the water and prevent them from gaining
a toehold. For planted tanks, this is not a good solution since the UV light
will also oxidize trace elements needed by the plants and will limit the
plant's growth potential. Unfortunately, conditions that are good for growing
plants are also good for growing algae. Fortunately, plants will usually
out-compete algae for the available nutrients. However, if there is an imbalance
of nutrients, algae will opportunistically use whatever is not used by the
higher order plants. Different algae will utilize different nutrients, causing
sporadic outbreaks of new algae types in apparently stable tanks when a
temporary imbalance occurs. An ounce of prevention is worth a pound of cure.
To avoid introducing a new algae type to a planted tank with new plants,
a simple bleach dip seems to work well. Mix 1 part bleach in 19 parts water
and dip the new plant in it for 2 minutes. Immediately rinse the plant in
running water, then immerse it water containing a chlorine remover to neutralize
any remaining bleach. This will kill the algae and only temporarily slow
down a healthy plant. Plants in poor condition may succumb to this treatment,
but they probably would not have lasted anyway. Algae Eaters The most effective
control of algae in a planted aquaria is via algae eating fish. It is especially
critical in the set up of a new tank to make sure algae does not get established
before the plants have had a chance to establish themselves. For this reason
and to help the biological filtration get established, it is recommended
that some hardy algae eaters are added right away.
Black sailfin mollies are excellent candidates for the break-in period of
a planted tank since they are cheap and easy to find. They are usually considered
expendable and are removed after a month or so. It is important to NOT FEED
THEM. If they are fed, they will not be quite so eager to consume algae.
When they are hungry, they are eager consumers of most algae types seen
during the break-in period.
Otocinclus are diligent algae eaters, but are best kept in schools due to
their small size. One per 10 gallons is a useful rule of thumb. Various
species of otos are seen in the shops at various times; most are good algae
eaters but some seem to prefer the slime coat on fish to algae. Unfortunately,
there seems to be no way to distinguish the "attack otos" from normal otos.
Otos seem to be very delicate fish, but this is probably due to capture
and shipping abuse rather than an inherent weakness. When a fish shop gets
some in, it is wise to wait a while before purchasing to account for die
offs. Most people report getting a dozen and having them die over a period
of a few months until just a couple are left. Those then seem to last for
a long time.
Plecostomus is the generic name for a wide range of sucker-mouth fish. Only
the smaller types are useful in a planted tank, since the larger varieties
tend to eat the plant right along with the algae. Two common types that
are useful are the "bristle-nose plecostomus" and the "clown plecostomus"
or Pekoltia. Both stay under 4" long and don't seem to cause too much plant
damage. Sometimes broad-leafed plants like Amazon swords will be scraped
a little too closely by the plecos, so they bear watching. Their diet can
be supplemented by blanched zucchini and bottom feeder tablets. They also
appreciate a chunk of driftwood in the aquarium to satisfy their need for
Siamese Algae Eater:
Do not confuse this fish with the Chinese Algae Eater, which is very aggressive and
does not eat algae. The siamese algae eater, Crossocheilus siamensis, is
a very good algae consumer and is known to eat black brush (red) algae. The only
problem is that these fish are hard to find in the United States. There are several
fish in this family. The most commonly seen is Epalzeorhynchos kallopterus, commonly
known as the Flying Fox. The Flying Fox is the more attractive of the two. It
tends to have a brownish body with a very distinct, sharp-edged black stripe with a distinct,
thin gold or bronze stripe above it. These tend to be very aggressive when
they are full grown and don't eat red algae (as far as one aquarium reference is
The other member is the Siamese Algae Eater. It is the same shape as the
Flying Fox but tends toward a silverish body with a somewhat ragged black
stripe.There may be an indistinct gold or bronze stripe above the black. These
are definitely not aggressive; they are good companions for discus and small tetras. When
they are young, the differences between E. kallopterus and C. siamensis may not be
very apparent, especially if you haven't seen both types together. Unfortunately,
most wholesalers don't sell fish to stores by their scientific name and the common
names that are used sometimes get pretty silly (like "siamese flying fox"). If
you really can't tell which one the store has, buy it anyway, but be prepared to sacrifice
it if it turns out to be the wrong kind (unless your fish aren't bothered by it, of course).
Amano Shrimp gained popularity when Japanese aquarist Takashi Amano
introduced them in his book 'Nature Aquarium World'. They are extremely
useful for algae control though they will not eat all kinds of algea.
Scientific name: Caridina japonica.
Farlowella are useful algae eaters although they are very sensitive to water
conditions.They type known as the Royal Farlowella will get too large for a plant tank
and may cause damage.
[This message was edited by Ghazanfar Ghori on Thu April 24 2003 at 02:17 PM.]