DR. DIETER BROCKMANN
not noticed any adverse effects on the livestock, apart
from one incident: A Tridacna crocea about 2.8 inches
(7 cm) long showed signs of degeneration in the experi-
ment described above, and died shortly afterward. It is
unlikely that this loss is related to lanthanum—anoth-
er T. crocea that lives in the same tank still shows no
symptoms. Until we have more information, I think we
should take great care when dosing lanthanum directly
into the aquarium.SUMMARY AND RECOMMENDATION
First of all, phosphate concentration can be controlled
and very effectively reduced with a lanthanum solu-
tion. Careful, moderate dosage leads to a slow decrease
in phosphate concentration, allow-
ing the animals to gradually adapt
to changing conditions. I would also
like to warn strongly against the
assumption that “more is better.”
Biological systems should only be
modified very slowly. Rapid changes
in elementary factors, such as water
parameters, can easily lead to losses,
especially among invertebrates.
The described experiment con-
firms that it is safe to use a lantha-
num solution in a reef aquarium to
reduce the phosphate concentration,
but it is important to take safety pre-
cautions until corresponding EC 50
values for stony and soft corals, gi-
ant clams, and fishes have been de-
termined. These precautions include:
1 Follow the manufacturer’s specifi-
cations and avoid overdosing.
2 Due to the strong binding capacity
of lanthanum, maintain constant
control of the phosphate concen-
tration. Phosphate concentrations
below 0.02–0.05 mg/L should be
avoided.
3 Phosphate concentration reduc-
tion should be very gradual, not
sudden.
4 Effective reduction of the phos-
phate concentration is achieved
only if the lanthanum solution
is added drop by drop to the
aquarium water at a location
where there is very high flow. The
bound-phosphate cloudiness will
be removed by physical filtration.
Filter socks and pads may need
cleaning after treatment with
lanthanum.
5 At the same time, the concentra-tion of lanthanum ions in the aquarium water should
be tested in order to avoid increasing it to known toxic
levels. Tests are available from Triton, ReefAnalytics,
and ATI.
6 Last, but not least, each individual must decide wheth-
er the conventional solid phosphate absorbers offered
by many manufacturers are better alternatives.SUGGESTION
To the producers of liquid lanthanum solutions for
aquariums: It would be very helpful if the concentration
of the La3+ ions were listed on the label. This would en-
able the aquarist to determine the required quantity for
the aquarium and avoid overdosing.