Live Sand
by
Jonathan Lowrie
Some definitions to begin
with:
Infauna
|
Animals that live within
sediments on seafloor bottom.
|
Epifauna
|
Benthic animals that crawl along
the bottom or are firmly attached to bottom structures.
|
Macrofauna
|
Macroscopic animals that live on
or in sediment.
|
Microfauna
|
Those animals less than 50
microns that live within the sediments.
|
Meiofauna
|
The animals between sizes. Also between spaces- these animals live
within the interstitial spaces of the sediments.
|
Closed System
|
System which has no connection
with outside environment. A typical
home aquaria.
|
Open System
|
A system with a direct
interchange with the outside environment.
|
NNR
|
Natural Nitrate Reduction. A concept of 'natural'
filtration using a plenum and live san layers.
|
Plenum
|
A space or cavity. In the case of
san beds, a raised space off the bottom of the aquarium with a barrier
covered with a thickness of sand.
|
'Natural'
|
A process that occurs in
captivity in much the same fashion as in nature.
|
Ecosystem
|
All the organisms in a biotic
community and the abiotic environmental factors they interact with.
|
Live Sand
|
Simply put: sand with living
organisms contained within the interstitial spaces, or on the sand grains.
|
SeaFloor
Characteristics
•
Seafloor characteristics are a crucial part of the habitat of benthic
organisms. As the substrate supports the
weight of many animals considerably more dense than seawater.
• The seafloor also acts as a mechanical
barrier to collect and accumulate plankton, waste material, and detritus. A variety of worms, echinoderms, mollusks,
and crustaceans obtain their nourishment from this organic matter.
•
Benthic organisms are adapted for a particular bottom type; and character of
life there, to a large extent, is dependent on the properties of bottom
substrate.
•
This bottom material varies from very solid rock to very soft, loose deposits.
•
The actual composition of the seafloor is determined principally by the amount
of energy available. In nature this is
through wind driven waves primarily.
• In an aquarium, it can be from the use of
auxiliary pumps.
•
Benthic animals play an important role in mixing and sorting of sediments by
their burrowing and sorting of the sediments by their burrowing and feeding
activities.
• Oxygen and water from the sediment surface
are transported down into the sediment through these tubes and burrows.
•
Further modification of sedimentary characteristics is accomplished via
cementing particles together to form tubes, and by compacting sediments
together as fecal pellets and castings.
•
The distributional patterns of benthic animals and plants are strongly
influenced by the form and texture of their substrate.
•
These factors determine effectiveness of locomotion, or for non-motile species,
the persistence of attachment to bottom.
Animal Substrate
Interaction
Because
of the different distributions, unique adaptations have developed allowing for
specialization to those environments.
•
The particle size and organic content of the bottom material limits the
versatility; and thus the distribution of specialized feeding habits.
Before
you say ‘huh?', allow me to explain in terms of our captive closed
systems. All the diverse habitat types
in nature all support a selective array of animal life.
• What
exists in one biotope, most probably will not exist in another. In our aquariums, this translates well into
the discussion of live rock and live sand.
•
Live rock is a solid substrate. It has a
variety of live within and about it.
From small sponges, tunicates, to corals.
•
Within may be algaes, bacteria, and more.
All of these animals and plants have adapted to life on a hard substrate
such as the live rock. Sand on the other
hand is a totally different environment
•
It is much softer, and will not offer the same advantages to most of the
animals. Yes, some will be able to make
the transition, and tolerate the new habitat, but many will not migrate to the
new habitat. Hence the reason why adding
live rock to ‘dead’ sand will not ultimately lead to a ‘live’sand bed.
Before the critics jump up and yell, let me
explain my opinion of ‘live’. Yes, the sand will have life in it.
But
will it have the typical life found within that format of sediment? No.
It has to come from somewhere, and sand
animals and plants as a rule don’t live on rock, and vice versa.
•
Suspension feeders depend on small plankton or detritus for nutrition. Filtering devices or sticky mucous nets are
employed to collect minute suspended food from the water. Suspension feeders generally
require clean water to prevent accumulation of indigestible particles.
•
Deposit feeders engulf masses of sediments and process them through their
digestive tract. They extract
nourishment through their digestive tract from the organic matter of the
sediment in much the same manner as an earthworm.
If
we are to keep obligate suspension feeders, or deposit feeders in our
aquariums, we must be sure to provide them the proper and suitable habitat to
thrive in.
Sediment Types
and Sorting
Many
reef sediments are terrigenous in origin (in Atlantic reefs). Terrigenous sediments are those originating
from terrestrial origins, and entering the ocean through streams and rivers.
The Atlantic Ocean has more large volume
rivers that dump literally millions of cubic feet per hour of terrigenous
sediments into the oceans. Much of this
falls along the Continental shelf, but some does reach the reef zones.
In the Pacific Ocean, there are fewer rivers
with huge outflows, as well as deep trenches to collect and accumulate this
sediment.
Another
sediment type of reefs is biogenic sediment.
Biogenic sediment is derived from living animal and plants. These are sediments formed from diatoms
skeletons, and skeletons of other animals and plants that have passed through
the water column.
Biogenic
sediments usually contain a high level of Calcium Carbonate.
Now,
again, how does all this relate to the home aquarium? Coarse sediments are very difficult for
animals to inhabit.
•
The sand grains are cutting, and have a considerable mass that can easily crush
the soft bodied animals. Most life here
tends to be tube burrowing worms, and mollusks.
• Many are considered meiofauna as they
exist in between sediment partakes as to prevent this destruction from
abrasion.
•
Finer sediments from sandy silt to mud typically have a rich fauna. Thousands of species can be found in healthy
sheltered mud flats and grass beds.
• These
natural sediment beds have another role as well. That role is as a mineral source. In nature, marine sediments will sometimes
release minerals that will precipitate to form irregular deposits on the
seafloor.
•
Coral skeletons, and Halimeda is composed of calcium carbonate is composed of
calcium carbonate in the form of aragonite.
While many of the red algaes, and forams have CaCO3 in the form of
calcite.
•
Calcium carbonate can exist in three forms- two of which are important to reef
systems. Those are calcite and
aragonite.
In the Aquarium
So
now I am back to the nature of the sand bed of the home aquarium. Typically, folks dump in a uniform size
gravel of aragonite based sand.
Problems:
• Inadequate habitat
Using a fine sand and a medium sand and a
coarse sand you can replicate the diversity of sediments to a limited extent.
Layers:
•
Good, Bad, or indifferent
Depth:
•
Deep?
•
Shallow?
•
Slopped?
A Mixed Sediment Filtration
System:
Another more complex method is to have a
mixed sediment system. This is involves
using a sump and or refugium as well.
Rather than go into great detail and stir up controversies, I will say
this: Refugia with seagrasses and
mangroves serve many useful purposes.
As a habitat for small shrimp, fish, mollusks,
etc. And as a means to filter the
aquarium. When I say filter- I also
include mechanical and biological filtration.
Seagrasses in nature act as a baffle for
sediment suspended in water, and will draw these sediments down to their
bases. In a properly flowing system the
seagrasses can serve much the same purpose at home.
NNR
Wait! Someone is bound to ask why? Why do we want to increase diversity if our
current NNR or other systems seem to work?
A
few comments:
• Live
sand will not form from dead sand.
Period.
Louis Pasteur proved the world wrong on
spontaneous generation, and it won't happen in your reef tank. No matter how good the live rock is, it won't
provide what is necessary for a healthy sand bed.
Does NNR work?
•
In many cases yes.
Is it the best system for
me?
•
Most often, no.
• Degrades over time
• Does not allow for diversification
• Artificial means to accomplish a
natural function
On shipping live sand.
Sand
is rough Its cuts, it grinds. And have you ever lifted 50 pounds of it?!
Imagine being a soft bodied annelid or a think shelled mollusk. And being grated, smashed, and smooshed by
the sand.
•
Collection
•
wait
•
Box
•
Tranship- in airplane
•
Wholesalers- stored
•
Fedex to you or stored
•
Retail channels
Ways to Improve
your Sand Bed:
• Add more benthic animals
Some sources may include Inland
Aquatics Detrivore kits
Indo
Pacific Sea Farms shrimp cultures
Brittle
stars, Holothurians, worms, etc.
• Increase particle type diversity
Add
more sand sizes
Add
deeper sediment layers
• Add sifters
Gobies,
other fish, etc.
• Feed and skimming
In
established reef, can consider skimmerless operation
Heavy feeding of phytoplankton and
zooplankton
Will
help establish microfaunal population
• Depth
At
least 6 to 8 inches. More if you can fit it.
Can
be hidden with bottom.
Wentworth Geometric Scale
|
|||
The phi scale is based on
the logarithmic transformation of a particle diameter (phi = logbase2
particle size in mm)
|
|||
Particle Type
|
Size
(mm)
|
Phi
units
|
|
Gravel
|
Boulder
|
>256
|
beyond -8.0
|
Cobble
|
256-64
|
-8.0 to -6.0
|
|
Pebble
|
64-4
|
-6.0 to -2.0
|
|
Fine Gravel
|
4-2
|
-2.0 to -1.0
|
|
Sand
|
Very coarse sand
|
2-1
|
-1.0 to 0
|
Coarse
sand
|
1-0.5
|
0 to
1.0
|
|
Medium Sand
|
0.5 - 0.2
|
1.0 to 2.0
|
|
Fine Sand
|
0.25 - 0.125
|
2.0 to 3.0
|
|
very fine sand
|
0.125 - 0.063
|
3.0 to 4.0
|
|
Silt
|
coarse silt
|
0.063 - 0.020
|
4.0 to 5.0
|
medium silt
|
0.020 -0.005
|
5.0 to 7.0
|
|
fine silt
|
0.004 -0.002
|
7.0 to
8.0
|
|
Clay
|
clay
|
<0.004
|
beyond 8
|
Composition of Reef Sand Communities
(Scoffin, et. al.,1985)
|
||
depth
|
region
|
composition
|
165 m
|
reef shelf edge slope
|
soft compacted sediment, medium
to fine sand
|
98 m
|
shelf edge
|
medium to coarse compacted sediments
|
71 m
|
outer shelf
|
coarse loose sediments, mainly
Halimeda
|
63 m
|
inter-reef location 1
|
mixed sediment sizes
|
69 m
|
inter-reef location 2
|
soft loose fine sand
|
46 m
|
leeward reef talus
|
well worn coarse sediments
|
40 m
|
lagoon, near reef
|
coarse unsorted sand
lagoon, away from reef medium to
fine sediments with much macrolife
|
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