NEWS107
26
ur aquarium-hobby forefathers
around 150 years ago had nobody
they could ask how to run an aquarium
successfully. They had to go out into the
wild andobservehow animals andplants
live.They then applied the results of their
observations to the aquarium. Sometime
thisworked,sometimesnot.Unfortunately
some of themost important knowledge
from back then has been forgotten or is
only justbeingdiscoveredagain.
Peat
Peat is formed inbogs.Bogs arewet areas
subject toheavyprecipitation,wherewater
collects and new plant growth is greater
than themassofdecayingdeadplantma-
terials. In thisway aboggrows constantly
O
Thewater is often coloreddeepbrown in thebiotopes of our aquarium fishes.The cause is secondary
plant substances.
Photos:FrankSchäfer
In the first three installments in thisserieswe lookedat thechemicalpara-
meters that caneasilybecheckedusingeverydayequipment andmeasu-
ringmethods:hardnessandpH.Unfortunately It isnotaseasywith thesub-
stances discussed in this installment.But never fear, even if someofwhat
follows sounds tingedwithalchemy: itworks!
Secondaryplant substances: the
powerofNature in theaquarium
byHeikoBlessin
upwards and thedeadvegetablematerial
is deposited in oxygen-depleted and/or
anaerobic layerswhere furtherbreakdown
via ,bacteriano longer takes place to any
noteworthydegree.The resultingmaterial
composed of only incompletely decayed
plant remains is known as peat. Peat can
derive fromall sortsofplants, inourclimes
for example fromheathers (
Calluna,Erica
),
sedges, andother acid-lovinggrasses,but
aboveall frompeatmoss (
Sphagnum
).Alt-
houghweCentral Europeansusuallyasso-
ciate the term bogs with Nordic regions,
that is incorrect.TheentireAmazon region,
forexample, isboggyand thestronglyaci-
dicpHofmanyof itswaters isattributable
to thepeaty,nutrient-poor soil. Peat is es-
sentiallynutrient-poor,butnotalwaysacid.
Whether thepH in theaquariumcanbe lo-
wered using peat depends on the peat
used.Only peat fromuplandbogs is suit-
able foracidification,andcanproduceapH
between3.5and4.5.
Secondary plant substances - evenwit-
hout lowering thepH?
But it isn't justacaseof thepHwhenweat-
tempt to influence thewaterwithnatural
substances andprovideour fisheswithas
natural anenvironment aspossible.When
we filter thewater over peat then it takes
onanamber- tobrown-colored tinge.This
is the result of so-called secondary plant
substances that are releasedby the peat.
The precise composition of secondary
plantsubstances ishighlyvariableandalso
subject todramatic local fluctuations. But
weareaware,empirically, fromexperience
that these secondary plant substances
haveanoverallbeneficialeffecton thevast
majority of freshwater fishes. Fishes in
whose aquariumwater these secondary
plant substances aredissolvedbecome ill
Water chemistry
The brown colorationof thewater in the Rio
Negro can be clearly seen in this photo of a
freshwaterdolphin. Photo:HeikoBlessin
