Q & A
spread rapidly, but there are
some steps you can take to
manage it if you’re dead set on
keeping it. Most importantly,
try and isolate the colony
when first adding it. Xenia
can reproduce and spread by
breaking off tiny offshoots of
the body onto neighbouring
rocks, and it doesn’t tend to
do so on sand as successfully.
Therefore, many aquarists
maintain it on its own rock
‘island’. Make sure this is
surrounded by sand and is
away from neighbouring rocks.
Whilst this doesn’t guarantee
that the colony won’t spread, it
does reduce the risk and if the
Xenia does spread it can make
it easier to deal with.
Be vigilant, keeping a close
eye on the sand as well as hard
substrates in the tank – and
don’t forget the glass itself. If
any new colonies spring up, get
rid of them them immediately
- this entails complete removal
of the Xenia by scraping off all
the living tissue. Ultimately,
the simplest way to discourage
Xenia from spreading is to not
introduce it in the first place,
but we can discourage it from
becoming a full-blown pest.
Clam Diet
What do Tridacnid
clams need to be fed?Tridacnid clams have
amazing nutritional
adaptations which
mean that they rely
on a range of approaches to
meet their needs, and it’s fair
to say that many aquarists
have successfully maintained
them without providing any
supplementary feeding at all.
Whilst (especially juvenile)
clams in the wild do appear to
feed on phytoplankton to asignificant degree, this may not
be required in the aquarium
providing conditions are right.
Most importantly, clams
need sufficient nutrients such
as nitrate and phosphate plus
dissolved and particulate
organic matter in addition to
the lighting needed for their
zooxanthellae; given these,
they can pretty much look after
themselves.
The zooxanthellae require
sufficient nitrate and
phosphate to photosynthesise,
and these provide sugars for
the clam – however, it has been
shown that clams will actually
harbour sufficient numbers of
symbionts that they can digest
thanks to roving amoeboid
cells. In this respect, they can
be viewed as zooxanthellae
‘farmers’. Extremely low
nutrient aquariums, therefore,
are not ideal as these don’t
support zooxanthellae growth
and I’ve seen some systems
with many clams and few
nutrient inputs where it’s been
necessary to actually add
phosphate and nitrates to keep
the clams healthy.
Clams may also absorb
nutrients such as nitrate and
phosphate directly from the
water, and they can filter out
suspended and particulate
matter and detritus. These can
be provided simply as a result
of maintaining fish with the
clams. Food particles and fish
faeces are an excellent food for
clams, and in general systems
with adequate fish loading can
provide adequate nutrition.
That’s not to say that clams
never need feeding – every
system is different and if
these needs can’t be met then
additional foods such as phyto
may be necessary. In general,
maintaining clams with suitable
fish bioloading and keeping
nutrients at sufficient levels are
all that’s needed.Q
A
Pulsing Xenia can take over the aquarium, but it’s possible to try and keep
it in check. Clams often do not need any supplementary feeding.
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