For
aquariums that lack the space below the main display, there are
several options. First, a separate tank can be placed beside,
behind or above the main display tank and plumbed with an overflow
box and/or bulkheads. This style can present some challenges, but
allows for the most visibility and enjoyment of the refugium.
Another option is a small hang-on-the-back refugium as illustrated
to the right. These smaller versions can be added to systems that
lack the appropriate space to include under the main display tank
or for aquarists that don’t want it in direct view. These most
often include a small circulation pump that draws aquarium water
from one end of an acrylic box and out the other end. Although
small in size, they can be effective in smaller aquariums up to 30
gallons.
Flow
rates can vary greatly in these systems, but most favor a high
turnover ratio, as much as 10x the water volume per hour. Larger
display tanks featuring corals and invertebrates can benefit from
even higher flow rates. In their natural environment, most marine
flora and fauna live in a dynamic place, with strong currents and
constantly changing tidal surge, so they are quite accustomed to
adapt to varied levels of water movement.
Most
available refugiums include a light, usually a 9w to 18w compact
fluorescent bulb. While the amount of light may be fine for some
macro algae, such as Chaetomorpha, Ulva and possibly a few
varieties of Caulerpa, it is often more desirable if space is
available, to upgrade to a higher output light source, such as t-5
fluorescents or for outstanding growth a 70 watt DE metal halide
fixture. Overall, it depends on the size of the refugium and what
the purpose of it will be. For most, the concept of a refugium is
to export nutrients quickly and efficiently, so why deprive the
algae of what it needs to thrive with a low light environment? On
the other hand, if the purpose of the refugium is to provide an
area for the reproduction of invertebrates to feed the main tank
then strong lighting to provide optimal growth is not necessary.
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