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NFC: Diatoms
Sorry I'm late with this one...but being something of an algae nerd, I
couldn't resist this thread.
Kevin wrote:
>The above statements are making an assumption that you are dealing with
>diatoms, which are often refered to as brown algae. There are other algae
>which are much less common which do have a brown shade.
Almost all "true" brown algae are marine. There are very few freshwater
species and they are relatively rare even in nature. Brown algae of either
water type tend to grow in cold waters...I mean really cold. Stranger
things have happened, but you probably have a much better chance of winning
a $200 million lottery than of finding genuine brown algae in a tank. Some
green mat-type algae will have a brownish/golden appearance in areas, but
green will also be evident. In other words, I believe Kevin is correct in
assuming diatoms infest Terry's tank. I also agree that they are easy to
control.
A little diatom trivia for you: Although diatoms are commonly (and
mistakenly) referred to as brown algae, their closest relatives are golden
algae. The skeleton (cell walls) of a diatom is made of hydrated silica
embedded in an organic matrix. Each wall is composed of two halves that
fit together like a shoe box and lid. Some diatoms can move around by
squirting stuff out of slits in their cell walls. There are about 10,000
known diatom species. Sorry, I couldn't resist --- I warned you I was an
algae nerd :)
The most common myth about diatoms is that they are caused by a certain
light level (some say low, others high) or just old bulbs. In my
experience, diatoms grow in all light levels from low to high whether the
bulb is old or not. Diatoms, like all algae plagues, are invariably caused
and sustained by excess nutrients in the water column. As Kevin has
already pointed out, silica is the most important of these in the case of
diatoms. However, removing silica, which can cost serious $$$, is not
necessarily the best method for tackling diatom infestations.
IME, the two best solutions for diatom control are Otocinclus catfish or
simply waiting them out. A half-dozen healthy otos will clear a
medium-sized tank (~55 gallon) in a few days and keep it clean
after. Waiting the diatoms out means scraping them from tank surfaces and
letting the filter and water changes remove them from the water column
which removes both the diatoms and consequently silica (and other consumed
nutrients) from the tank water. Eventually, the plague will peak and then
fade away rather quickly. For the impatient, there are silica removal
resins that will take the silica out of water, but they can be a pain and
are not cost effective. Or you could use a reverse osmosis filter to
remove practically all minerals from tap water, but RO can cause as many
problems as it cures in some cases and it is certainly expensive both in
time and money.
Terry, I wouldn't worry about diatoms too much especially since your tank
is young. They are common in the unstable environment of a new
setup. Just keep up on regular maintenance like you've been doing. The
diatoms will clear up eventually. I'd go ahead and get some otos
too. They are one of the most useful fish in the hobby and few fish can
keep up with them at removing mat-type algae. I never have to wipe the
glass, etc. in the tanks I keep them in. They make excellent community
tank residents too, but don't put them in with overly aggressive or larger
meat-eating fish. Otos are spunky but they're small.
I also recommend live plants for controlling algae, but that's a whole
nuther can of worms (and a whole nuther email list ;).
Chuck
Chuck Huffine
Knoxville, Tennessee USA
mailto:grendel at usit_net
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