the aquarium, transported to the external
tank, and finally returned to the main tank.
This invariably involves a certain risk of
mishap. There is no doubt that it is safer
if the water never leaves the aquarium at
all—intentionally or otherwise! A further
disadvantage is the noise made by the water gurgling down from the main tank into
the filter tank. However, there are now a
number of very low-noise solutions to this,
and in the final analysis it isn’t necessary to
move a large amount of water between the
two tanks in order to link them together; if
the volume of the filter tank is turned over
twice per hour, for example, that is perfectly
adequate. As a rule, the more water we move
around per hour the louder the process is.
Another potential problem with a typical sump is that if the down-pipe becomes
blocked, but water continues to be pumped
from the sump up into the main tank, the
latter may overflow. This can also happen
with the filter tank if there is a power outage or the return pump fails, and water
continues to flow down from the main tank
until the spare capacity of the sump is exhausted. For this reason, the system must
be designed so that both main tank and filter tank, when filled to the desired levels,
have sufficient spare capacity to contain the
amounts of water that may continue to arrive there in the event of any problem. If
this isn’t possible, then the main tank and
sump should be protected against unforeseen overfilling by installing float-operated switches that
will, in an emergency, disconnect the relevant return
pump(s) from the water supply.
left and following page: d. knop; this page: werkfoto giesemann
Sumps also costs money, not only to set up but also
to run, as in the final analysis we are using electrical
energy around the clock to pump the water that gravity
has transported down to the sump back up to the main
tank. Depending on the pumping equipment used, this
process will normally even warm the water to a certain
extent, as the majority of pump models are wholly or
partially water-cooled. This can be an advantage or a disadvantage, depending on the ambient temperature.
A sump undoubtedly makes the main aquarium look
more attractive, and is more hi-tech and hence more
interesting for many aquarists. But it is simultaneously
more expensive, requires more equipment, and involves
greater risk. Every aquarist needs to weigh up for him- or
herself whether the benefits are worth the investment
and the risk.
In a small aquarium with a volume of around 21 gallons ( 80 L), it is certainly an attractive idea not to have
to accommodate equipment such as a protein skimmer
this 17-gallon (65-l) aquarium
does considerably better with a
sump, which permits extensive
water treatment and makes it
possible to keep small, delicate
creatures whose metabolic
products pollute the water more
heavily. it would be difficult to
accommodate the necessary
filter equipment in such a small
aquarium.
in the tank. In a 264-gallon ( 1,000-L) aquarium, however, it should be easy to find a place in one of the rear
corners where a compartment for housing equipment
can be constructed using two extra pieces of glass. We
will show you just how easy this is in a forthcoming issue
of this magazine.
If you do decide to install a sump, you should note
the following points:
• Keep the turnover volume as low as possible. It is
pointless to circulate 1,055 gallons ( 4,000 L) of water or
more hourly between a 132-gallon (500-L) main aquar-
ium and a 26-gallon (100-L) filter tank. That would
cause loud gurgling around the clock, guzzle electricity,
heat the water, and also rapidly flood your home in the
event of a power outage or equipment failure. An effec-
tive turnover rate of 52 gallons (200 L) per hour is per-
fectly adequate for the tank sizes cited.
• Carefully calculate the amount of extra water the
sump can cope with if the return pump stops working,
as in that event, a certain amount of water will continue to run down from above. You can not only calculate this but also test it by simply switching off the re-
