The Environmental Gradient
Filter Feeder Zones
The filter feeder zone describes both the semi-exposed and semi-cryptic zones within
nature and within the Environmental Gradient concept. I have decided to combine these
two zones into one for various reasons. Aquarists can learn what is going on within a
zonal system much easier if there are just three distinct zones. Science is just now
analysing and documenting the parameters of semi-cryptic and semi-exposed habitats
in nature. It will be a few more years before we know for example if a particular sea
squirt species is more often found within a semi-cryptic or a semi-exposed zone. Another
reason is that a three zone EG system is very easy to setup and establish within a
captive system. Some low light to weak light organisms can survive within the filter
feeder zone, but it is dominated by the non-photosynthetic filter feeders that catch and
consume large particulate matter. I am setting up 4-125 gallon aquariums during the
summer of 2002 that have well defined filter feeder zones. I will be adding information
to this page as more is learned. Volume 2 of the CMAT book series will also contain a
formal definition of this zone.
