The Environmental Gradient
Sea Squirts
The Sea Squirts that are utilized within the EG system can be either cryptic sea squirts
placed within the cryptic zone or semi-cryptic to semi-exposed sea squirts placed
within the filter feeder zone. Sea squirts are very prolific on tropical reefs and
some species even inhabit the exposed zones. Most of the larger sea squirts that
have been imported for the captive hobby are from the exposed zone. They require
stronger currents. The cryptic to semi-exposed sea squirts require weaker currents.
Some species (mainly green colored and some pink colored) contain a symbiotic algae,
but most do not contain algae and are not photosynthetic. Sea squirts primarily consume
phytoplankton, fine particulate matter along with very fine particulate matter and some
bacteria. Sea squirts are also able to consume some dissolved organics through the
process of iodine binding. They can be colonial with many small zooids or solitary
with one large zooid. Cryptic sea squirts do not possess an ability to shield themselves
from UV light and will be seriously affected by exposure to shallow water light. Sea squirts are negatively affected by very turbid water and prolonged periods of exposure to water
containing high amounts of suspended sediments. They are able to handle slightly turbid
water and some sediment suspension better then cryptic sponges. This allows many sea
squirt species to survive within the filter feeder zone.
