|
|
 |
|
|
|
|
Creating
a Healthy Environment
for Ornamental Fish |
|
Recommended
Parameters: |
Essential Water Quality Parameters
To be successful with any aquatic environment supporting
fish, retailers and hobbyists must know how to achieve
and maintain a suitable aquatic environment. Fish that
are pale
in color and stressed are usually suffering from poor
water quality. Symptoms of poor water quality are unacceptable
pH, nitrite, nitrate, low dissolved oxygen levels, and
fluctuating water temperatures. Proper
circulation and filtration have much to do with establishing
consistently good water quality. Water quality parameters
below acceptable levels will stress the fish in a pond
or retail system, depleting dissolved oxygen levels
and causing infection or even death. Applying a few
simple modes of filtration, conducting periodical water
tests and providing routine maintenance will ensure
a successful, more profitable retail fish system.
|
|
Dissolved Oxygen:
8mg O2 @ water temp 70oF
pH:
7.2 to 8.5
Temperature:
65o to 70oF
Salinity:
0.3% to 0.4%
Ammonia:
Less than 0.5 ppm
Nitrite:
Less than 0.25 ppm |
|
 |
|
Dissolved
Oxygen
Air consists of 21 percent oxygen and approximately
75 percent nitrogen by volume. Oxygen dissolves poorly
in water and can only exist there at a low concentration.
Even so, dissolved oxygen is essential for the respiration
of animals and bacteria in the aquatic environment.
Ponds and aquatic systems containing free oxygen molecules
are aerobic; those without are anaerobic. Anaerobic
aquatic systems will not support higher life forms such
as fish and bacteria. They are characterized by the
presence of noxious chemicals such as hydrogen sulfide,
which can cause odors. Anaerobic conditions are normally
found in bottom sediments and dirty filters. |
|
pH
pH ranges between 0 and 14 in water.
Water with a pH value of 7 is said to be neutral while
water with a pH below 7
is acidic and pH levels above 7 are
considered alkaline. pH levels between
7.2 to 8.5 are considered acceptable.
Temperature
Water temperature is sensitive to atmospheric temperature.
It is influenced by the Sun's energy, water depth, water
circulation, pump motor heat, and heat from other mechanical
devices. Water temperature directly impacts the level
of dissolved oxygen retention. A water temperature exceeding
75oF can inhibit the ability of fresh water
to retain an acceptable level of dissolved oxygen. |
|
|
Salinity
Fish are sensitive to the salt content of their waters. Each
species has evolved from a system that maintains a constant
salt ion balance in its bloodstream through movement of salts
and water across the gill membranes. Fresh and saltwater species
generally show poor tolerance to large changes in water salinity.
Salts may be added to fish ponds at predetermined levels;
doing so can fight off infection and parasites.
|
|
Nitrite
Nitrite is an intermediate product of the aerobic nitrification
bacterial process. It is very toxic to fish because
it oxidizes hemoglobin to methemoglobin in the blood
(as carbon monoxide does with human hemoglobin), turning
the blood and gills brown and hindering respiration.
Ammonia
Too much ammonia can cause serious problems in pond
management. Fish suffering from ammonia toxicity typically
stop eating and become lethargic. Several causes can
increase total ammonia nitrogen levels in ponds. If
the fish are overfed, uneaten food sinks to the bottom,
decays, and releases ammonia, increasing the load on
the nitrifying bacteria in the pond and filter. Too
many fish in the pond or system can mean that the wastes
produced exceed the capacity of the nitrifying bacteria.
The pond/retail system or filter may not be operating
properly and may contain abnormal amounts of captured
solids, depleting dissolved oxygen levels and overburdening
nitrifying bacteria colonies. |
 |
|
| |
Filter
Terminology
Mechanical
Filtration
Mechanical filtration is the separation of solid waste
from water, using a filter medium to capture and hold
waste until it is removed from the filter. The many
available styles of filters and filter media include
polyester woven pads, reticulated foam, silica sand
and floating bead media. Types of mechanical filtration
include gravity separation (settling devices) and pressure
filters such as bead or sand filters.
Organic
solid waste left in a pond or retail system will quickly
decompose into harmful elements, lowering the water
quality and stressing the fish. Decomposing waste consumes
precious dissolved oxygen in the water. It's especially
dangerous during the warm months, when water temperature
within the pond or retail system may exceed 82oF.
Rotting solid waste also increases the load on the biological
(beneficial bacteria) filtering process, creating the
potential for ammonia and nitrite fluctuations that
are very stressful to fish. It is absolutely critical
to routinely trap and remove solid waste (at least weekly).
Biological
Biological filtration is a natural process. Colonizing
Beneficial Aerobic Bacteria (oxygen consuming nitrifying
bacteria) transform harmful toxins (ammonia/nitrite)
into less harmful elements (nitrate) through the process
of nitrification. The biological filtering process within
an aquatic environment is not restricted to the biological
filter. Rather, nitrifying bacteria colonize on surfaces
inside the pond such as rocks, liner and submerged plumbing/hoses.
During the start-up of a pond or retail fish system,
the pond keeper or employee must track nitrification
using an ammonia, nitrite and nitrate test kit. During
testing, ammonia will appear first. A week or so later,
nitrite will be present and finally, a few weeks later,
nitrate. The time it takes to complete the nitrification
cycle is largely determined by waste load and water
temperature within the system. The time is usually four
to six weeks.
Chemical
Chemical filtration employs media such as activated
carbon to absorb dissolved organic wastes or toxins
in the water. While activated carbon effectively absorbs
dissolved organic waste, it is a temporary and potentially
expensive solution. Other media available include zeolites
and resin compounds, which absorb ammonia, nitrate,
phosphate and chlorine from the water. |
|
|
Ultraviolet
Sterilization |
For
decades ultraviolet sterilization has been used as a microorganism
disinfectant. Using a low-pressure mercury vapor germicidal
lamp, input watts supplied to the lamp create an
electrical arc with the mercury inside. This reaction
creates UVC
light. The UVC light at 250nm to 280nm (the germicidal
effectiveness curve), when applied to microorganisms such
as bacteria and protozoa, is very effective at altering
their DNA,
disabling them from reproducing, or even destroying them. |
 |
Microorganisms
vary in type and size. For example, bacteria range
in size from 0.2 to 1.5 µm
while protozoa may reach a size of
10mm. Identifying the targeted microorganism, and matching
its
type and size to its established UV exposure rate, are
prerequisites for destroying that particular microorganism.
In order for UV sterilization to be effective, the UVC
( UV radiation @ 250-280nm) energy must penetrate the
microorganisms cell wall/cell membrane and destroy the
nuclear material (see adjacent diagram).
|
µWs/cm2
= UV exposure
• Common Bacteria - 15,000 µWs/cm2
• Waterborne Algae - 22,000 µWs/cm2
• Protozoa - Above 90,000 µWs/cm2 |
GUIDE |
nm
- nanometer
µm - microns |
|
|
Successful UV sterilization in a water application requires
the targeted waterborne microorganism to be in direct
contact with the UVC light being produced by the UV lamp
for a specific amount of time (UV exposure rate). Established
UV exposure rates for many types of waterborne microorganisms
must be applied to achieve successful UV sterilization. |
|
|
Water
Circulation
Water circulation is a critical filtering factor. Flowing
water agitates and suspends solid waste
in the pond or retail fish system, moving it to the mechanical
filter where it is trapped, held and removed. In sufficient
water circulation, a common problem associated with ponds
and retail fish systems, is caused by inadequate pump capacity,
improper plumbing or both. When planning your system, pay
close attention to the pump's capacity and the diameter of
pipe used to plumb the system. Filtered water returning to
the system should create a gentle current and be directed
(using PVC fittings) so as to subtly force water downward
to the bottom of the tank or pond, suspending all solids.
Proper water circulation will help to prevent solid waste
from settling on the bottom of the pond or tanks, while providing
current that most fish enjoy. For a pond application, we recommend
a general turnover rate of once every three hours; for a recirculating
retail system we recommend a minimum turnover rate of twice
per hour. |
|
Maintenance
Regardless of the filter system
you choose, routine maintenance is an essential part
of the filter’s operation. All mechanical filters
must be cleaned frequently. Solid waste that settles
on the bottom
of a pond or retail fish tank must
be removed. Fluctuating fish loads commonly associated
with retail fish systems require routine water testing,
so that employees will be alerted to potential ammonia
and nitrite fluctuations.
|
 |
|
Decorative rocks and pebbles placed on the bottom of a pond
are not recommended! Decorative stone or pebbles accumulate
solid waste, allowing it to decompose and foul the system.
Decomposing solid waste lowers water quality, including its
capacity to maintain acceptable dissolved oxygen levels.
Establishing
good maintenance procedures is essential to the long-term
success of any aquatic system. In a retail fish system, high
fish density usually imitates an aquaculture application rather
than an ornamental pond. Employees must understand the importance
of maintenance, and correct procedures must be followed to
the letter. |
|
|
