Exotics Top Topics - Environmental Aquatic Disorders Flashcards
key health issues related to environmental factors in fish are related to what?
ammonia, nitrite, pH, temperature, bicarbonate, heavy metals, & dissolved gases
T/F: most health problems in fish are made worse by poor water quality or inappropriate water temperatures
true
what is critical in preventing environmental aquatic diseases in fish?
regular tank maintenance & quality water monitoring are critical
what is the classic case presentation of acute new tank syndrome?
convulsive swimming/spinning
what is the classic case presentation of sub-acute to chronic new tank syndrome?
lethargy, anorexia, increased respiration, & death
damaged gills
what is the pathophysiology of new tank syndrome?
ammonia toxicity or nitrite toxicity - high levels of toxic/un-ionized ammonia or nitrite caused by an underdeveloped biofilter
biofilter contains bacteria needed to emtabolize toxic ammonia waste from fish/uneaten food
nitrite is an intermediate metabolite in the multi-step nitrification of NH3 to nitrate
nitrite can cause brown blood disease at elevated concentration (methemoglobinemia) because methemoglobin forms as a result of nitrite binding to hemoglobin & disrupting the ability for RBC to bind oxygen - RBC with methemoglobin can make blood look brown instead of red, but normal appearing blood may still have significant amounts of non-functional RBC
how is new tank syndrome diagnosed?
measure ammonia & nitrate levels
how is new tank syndrome treated?
assuming pH of water source & system water are similar, consider a water change to drop un-ionized ammonia levels (to < 0.05mg/L) and to reduce nitrite levels
how is new tank syndrome prevented?
add commercially available nitrifying bacteria to a tank with no fish & feeding the bacteria with fish food or ammonium chloride
bacteria can also be added using water, filter media, or substrate from an established healthy tank with no major history of disease (still biosecurity risk)
how long can it take for a tank to develop its own healthy biofilter to process nitrogenous waste?
up to 6 weeks or more
what is the classic case presentation of of old tank syndrome in a marine system?
may see algal growth, recession of corals
what is the classic case presentation of of old tank syndrome in a freshwater system?
may be no obvious tank problems or disease fish prior to a system crash
what is mortality like in old tank syndrome?
high mortality rates in a previously thriving, long-established tank - possible changes in appetite, attitude, or activity
what is the etiology of old tank syndrome?
primarily a problem of very low to non-existent alkalinity
what is the pathophysiology of old tank syndrome?
alkalinity includes several different buffer compounds (especially bicarbonate) that not only buffers but acts as a carbon source for the nitrifying bacteria in the biofilter which further acidify the water as they use up the bicarb
biofilter is less efficient as the pH drops and when alkalinity is completely consumed pH can go below 4 & cause a system crash - happens readily if source of water has low alkalinity or may take months to years after the biofilter has been cycled if water quality is not tested regularly
in addition, high organic loads (unsiphoned debris) will acidify the water as it breaks down
how is old tank syndrome diagnosed? how is it prevented?
use a water test kit to monitor nitrogen metabolite levels, pH, & alkalinity - may see total ammonia nitrogen 3mg/L->20mg/L, extremely low pH of < 5-6, & low to zero alkalinity
do water tests weekly/monthly depending on starting parameters, fish load, feeding, & managing
how is old tank syndrome treated?
change the water & add products to bind NH3 to prevent ammonia toxicity as the pH increases (takes weeks) using binding products with caution
stepped approach - changing out water over a week, using a clean source with a pH that is 7 or lower until most of the total ammonia nitrogen has been replaced & then increase pH using source water
how is old tank syndrome prevented?
good tank maintenance including siphoning of debris/cleaning & regular water testing - add new fish/coral slowly & incrementally, large frequent water changes, & iron-based phosphate removing resins
T/F: old tank syndrome is less common than new tank syndrome
true
why does old tank syndrome usually occur?
usually due to tank mismanagement or benign neglect but strongly driven by alkalinity & pH
what is the classic case presentation of subacute chlorine toxicosis?
cloudy eyes, gill inflammation/necrosis, increased respiration/piping at the surface, excess mucus covering gills, & lethargy
what is the classic acute case presentation of chlorine toxicosis?
sudden death
what is the etiology of chlorine toxicosis?
chlorine is commonly used to disinfect tanks but it is toxic
how is chlorine toxicosis diagnosed?
measure free & total chlorine using colorimetric test - should be zero, but can get false negatives if the sample is transported for testing (test on site)
how is chlorine toxicosis treated?
dechlorination/chlorine binding products
affected fish may benefit from addition of salt (3-5 g/L for freshwater) or reduction of salinity (25g/L for marine systems) to help relieve osmoregulatory burden resulting from damage to gills/skin
what puts fish at an increased risk of getting chlorine toxicosis?
increased risk if the water source contains chlorine/chloramine & dechlorinating products aren’t used during a routine water change
T/F: chlorine toxicosis is not an uncommon cause of acute mortalities in tanks or ponds
true
what is the classic case presentation of acute on chronic heavy metal toxicity in fish caused by heavy metals/zinc/copper toxicosis?
mortality
what is the classic case presentation of acute copper toxicosis in fish?
blunted gills, abnormal lateral line, distress, darkening, lethargy, & incoordination
what is the etiology of heavy metal toxicity in fish?
causes derangement of osmoregulatory capacity & electrolyte balance (calcium & sodium levels) & zinc toxicosis can fatally inhibit calcium uptake
copper may also alter sodium/calcium uptake causing damage to gill tissue & causing immunosuppression
how is heavy metal toxicity diagnosed in fish?
measure heavy metal concentrations & compare to source water & published fish toxicity information
how is zinc toxicosis in fish treated? how is it prevented?
no known treatment
do not use zinc in tanks or allow coins in tanks/ponds
how is copper toxicosis in fish treated? how is it prevented?
use chelating compounds & activated carbon filters - if source is known to have copper piping, prevent by running the water before filling the aquarium/tank & checking copper levels
what is a common scenario for copper toxicosis in fish?
improper use of copper for parasite treatments in fresh or salt water systems or less commonly, due to the addition of water that has been standing on copper pipes
what is a commonly seen scenario for zinc toxicosis in fish?
using stainless steel or zinc-galvanized tanks (aquaculture) or throwing pennies into an exhibit pond
what is the risk for heavy metal toxicity from copper if the pH of water in a system decreases?
copper bound to substrate in a system may be released if pH decreases
what gases cause gas bubble disease of fish?
N2 or less commonly O2
what is the the classic case presentation of gas bubble disease in fish?
exophthalmos, gas bubbles in the eyes, skin, gill capillaries, & fins, lethargy, buoyancy issues, & sudden mortality
what is the etiology of gas bubble disease? what is the pathophysiology of the disease?
supersaturation of water with dissolved nitrogen gas or O2
similar pathology to the bends - gas under pressure is taken up by the fish’s body but then bubbles escape the blood/fluids & form air emboli that block blood vessels & damage tissues
how is gas bubble disease diagnosed in fish?
use a saturometer/total gas pressure meter to measure dissolved gases in water & calculate N2 gas saturation
how is gas bubble disease treated?
identify & correct the source of supersaturated water if occurring in a system - use degasification units to treat flow through systems in which source water is supersaturated
correct underlying cause (water source or leaking pumps)
degasification in larger recirculating aquaculture systems is also recommended to remove CO2 as well as low levels of N2
when does gas bubble disease most commonly occur?
when well water is high in N2 gas is used to fill the tank or if the system’s water pump has a leak & is sucking in air & pressurizing it into the water
what are the 3 main categories of pH issues causing disease in fish?
accidental application of hydrated lime to a pond causing a rapid increase in pH to > 10
old tank syndrome
high CO2 levels decreasing pH
how are pH issues causing disease in fish diagnosed?
TA <50 = low, inadequate to buffer pH changes
ideal is 100 for freshwater & 150-200 mg/L for saltwater
measure total alkalinity (amount of bicarb in the system vs total water hardness measures calcium & other divalent cations)
how is high water CO2 (> 12mg/L) treated for fish?
degasification - increased aeration or a separate unit that allows for increased gas exchange) to help remove CO2 gas & increase pH
how is low total alkalinity treated for fish?
add limestone or dolomite to ponds to increase the alkalinity & hardness - small amount can be added to the substrate or sump of an aquarium
or add baking soda
what are 2 very important drivers of water pH for fish environmental diseases?
alkalinity & CO2
when is CO2 concentration usually lowest in a pond with plants/algae?
lowest in late afternoon because all algae use up CO2 through photosynthesis & highest first thing in the morning
CO2 levels are inversely related to dissolved oxygen content & pH
T/F: most freshwater fish have an acceptable range of pH but even within range, large fluctuations can be disturbing
true
what is alkalinity?
a measure of buffering capacity of water against acid - measures among other buffer compounds, bicarbonate which is the key buffer
