by George Booth
descriptions and control techniques are for common types of algae
found in freshwater aquaria.
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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.
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
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.
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 algae eaters.
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 "Algae-Destroyer").
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
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 it.
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
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 cellulose.
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 concerned). 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