NEWS107
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less frequently and exhibit more intense
colors.However it isn't alwaysdesirable to
implement thiseffect incombinationwith
anacidpH,as in the final analysis someof
ouraquarium fishes toleratea lowpHonly
badly.
Variousmanufacturersofferproducts that
add the substances describedhere to the
aquarium water, color the latter a light
amber,anddon't actuallyhaveapH-lowe-
ring effect.But oak extract, for example, is
often added because of demand from
aquarists and there is then apH-lowering
effect.Hence it is important to read thema-
nufacturer's instructionscarefully:does the
producthaveapH-loweringeffectornot?
InLakeMalawiorLakeTanganyikaaquaria
theadditionof suchproductswouldhave
an unnatural effect as thewater in these
lakes isn'tmeasurably influencedbyhumic
substances.
Leaf litter
Dead leaves from treeshaveapart toplay
ineveryaquarium,as theynotonly release
secondary plant substances,which in the
case of Sea Almond (
Terminalia catappa
)
andWalnut (
Juglansregia
)evenhavea the-
rapeuticeffect in the treatment of various
fishdiseases,but also represent avery im-
portant and often undervalued compo-
nent in thenaturaldietofverymanyaqua-
rium fishes.Althoughdead leaves are rat-
her nutrient-poor per se, they fall in such
largequantitiesas to form thebasisofnu-
merousnutritionalpyramids inaquaticsy-
stems.The leaves themselvesarealsocon-
sumedbyaquarium livestock, forexample
manysuckermouthcatfishes (
Loricariidae
),
characins (
Characidae
), and cyprinids (
Cy-
prinidae
), and leaf litter is even themain
foodof somecrustaceans.But farmore im-
portant for themajorityof fishesanddwarf
shrimps is the biocover of bacteria, fungi,
andothermicro-organisms on the leaves.
Very large amounts of detritus, ie the
breakdown products of dead plants and
animals,are foundeven in thestomachsof
fishspecies thatareknown from theaqua-
riumhobby tobepredominantlycarnivor-
ous (flesh-eating), for exampledwarf cich-
lids (
Apistogramma
);and the leavesof trees
are themost importantsourcesofdetritus.
Thusdead leaves represent thebasisof the
dietof verymanypopularaquariumoccu-
pants in thewild.
The leavesofalmostall treespeciescanbe
used as long as they are knownnot tobe
poisonous.It is,however,very important to
use only leaves that have already fallen
from the tree.Freshlypicked leavescanbe
dried and used as food for certain aqua-
riumoccupants,but theyhaveaquitedif-
ferent make-up to fallen leaves as trees
cannot afford to waste nutrients. Hence
theyextract asmanynutrients aspossible
from their leavesbeforeshedding them (in
autumn in temperatezones,before thedry
season in the tropics).So ifyou insteaduse
dried,fresh leaves,whicharevery rich insu-
gars andother nutrients, thenwater clou-
ding may result from bacteria or other
micro-organisms processing these nu-
trients.Thatdoesn'tnecessarilyhave tobe
harmful to the fishes, but it isn't healthy
and is far fromdesirable. SeaAlmond lea-
ves are available from varies suppliers in
the trade.
Inconclusion itcanbesaid that secondary
plant substances represent a very impor-
tant component ofwater chemistry inna-
turalwatersand that theyare increasingly
receiving recognitionashelping toprevent
many problems in the aquarium andma-
king theaquariumhabitatmoreamenable
for its occupants. And the industry has
realized this such thatmore andmore of
theproductsmentionedaboveareavaila-
ble in the pet trade. Experiment without
worries, as the nice thing about these na-
turalproducts is that ifusedcorrectly there
are no noteworthy side-effects to be ex-
pected.
Poecilocharaxweitzmani,
a typical blackwater fish.
Notonly incentral Europe,but also in theTro-
pics,thedead leaves that fall into thewaterare
oneof themost importantsourcesofnutrients
for theecosystem.
