VISITOR'S QUESTIONS
12... Algae Bloom
Algae bloom, and the "bacteria bloom" that I spoke
of last email, both result from excess nutrients in the water, however
algae bloom is also a result of too much light. This is not necessarily
attributed to the aquarium lighting but also intense room lighting and
direct sunlight.
It is the free floating planktonic single celled algae
growing at a phenomenal rate that turns the water green, often referred
to as "green water". The cause is always the same excess light and nutrients
(nitrates) often resulting from overfeeding and uneaten food. Obtain
a nitrate reading to confirm this.
Whenever an aquarium is set up a number of cycles occur,
some you probably know of, such as the nitrogen cycle. A phosphorous
cycle also occurs, and may be stimulated if phosphate buffers are over-used
when there is excess nitrates present, therefore you may have compounded
the situation by adding a phosphate remover in your filter.
You have got the right idea by performing water changes,
however, it seems as though you have still got the nutrient problem,
therefore the water changes are providing little or no help in clearing
the water.
Algae spores will thrive in nutrient rich water, an algae bloom can
become so severe that the content of your aquarium can literally vanish
in the green water.
Algae is another form of plant life and will consume
oxygen at night during photosynthesis. If your algae bloom is severe,
adequate oxygenation should be provided during the lights off period
at night-time, it is possible for a severe algae bloom to deplete the
tank of oxygen.
If algae is another form of plant life you will be
right in thinking that it requires exactly the same conditions as plants
to survive i.e. light and nutrients. Therefore to rid yourself of the
algae you need to remove the things that it needs to survive.
Dying organic matter create just the right nutrients
algae need for survival, so the filter should be rinsed more frequently
during an algae bloom, eliminating some of the decaying matter. Vacuuming
the gravel will also help.
Reduce your aquarium lighting and reduce the length of time it is on.
Do not overfeed your fish tank.
Other possibilities include adding very strong filtration,
you could put a large internal filter in the tank, frequently rinsing
its filtration media.
This may sound strange, however, put daphnia in the
tank. These are minute crustaceans that are actually a favourite of
fishes. If you can find a supplier of live daphnia they will eat off
your green water in no time -- that is, if the fishes don't eat the
daphnia first, in this case refrain from feeding the fishes yourself.
Live plants are always a good option because they absorb the nutrients
that the green algae will otherwise thrive on.
In summary, the only way to prevent or solve an algae
bloom is by controlling excess nutrients.
You also mention that you are struggling to keep the pH up above 6.5,
my solution to this is to add coral gravel (not coral sand, it's too
fine) in the filter chamber. Be very careful if you decide to try this,
you should only put a small amount in at a time, try a teaspoon full
and check your pH daily for three or four days before adding more, until
the desired pH is achieved. I should add that this will also raise the
hardness of the water.
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