There are lot of diseases that fish can get from feeds which include food poisoning (especially when decayed feeds are served), Salmonellossis etc. the best thing is to always serve non- contaminated feeds to your fish and also report any sign noticed on your fish farm to your consultant who will help diagnose the source of the disease and prescribe adequate treatment.
The Dangers of Uneaten Fish Food
Let’s face it, it’s fun to feed our fish! It’s one of the few ways we get to interact with them, and it’s a great way to get shy fish to come out so we can observe them.
Unfortunately, overfeeding is not only detrimental to your fish, but also to the overall health and well-being of your aquarium. Here are some negative effects uneaten food can have on your aquarium:
- Uneaten fish food releases toxic ammonia and nitrite as it decomposes. This is especially dangerous to newer aquariums where the nitrifying bacteria that gets rid of these toxins hasn’t had a chance to fully develop. High ammonia and/or nitrite levels can stress and even kill your fish. This problem is even more severe in small aquariums where toxins can reach lethal levels quickly.
- The decomposition process uses oxygen, which lowers the dissolved oxygen content (DO) in the water and stresses your fish. Since DO decreases at higher temperatures, the effects are more severe in warmer aquariums that are in the upper 70’s to mid-80’s. Poor water circulation compounds the problem.
- The breakdown of organic material lowers pH by releasing carbon dioxide, which is converted to carbonic acid in water. In soft water aquariums or those with low buffering capacity, pH can quickly drop below the safe range for many fish species, especially those that prefer more alkaline or basic conditions.
- Uneaten food can clog your filter, decreasing its efficiency and reducing circulation in the aquarium. This may result in a low dissolved oxygen content, a drop in pH, a rise in ammonia and nitrite levels, and general stress to your fish. Decomposing fish food also offers a place for mold and fungus to grow.
- Excess food causes a rise in nitrate and phosphate levels, which contributes to increased algae growth. Poor water quality also stunts your fishes’ growth, causing their colors to fade and lowers their resistance to disease.
- Fish can suffer from obesity and the negative effects on their liver, kidneys and other internal organs.
The Feed Conversion Ratio, a major indicator of feed efficiency in fish farming
The feed conversion ratio is an indicator that is commonly used in all types of farming, as well as in the field of research. It can provide a good indication of how efficient a feed or a feeding strategy can be.
In the context of aquaculture, the F.C.R. is calculated as follows: F.C.R. = Feed given / Animal weight gain.
In other words, the F.C.R. is the mathematical relationship between the input of the feed that has been fed and the weight gain of a population. There are no measurement units used in writing the F.C.R. The lower the F.C.R, the higher the weight gain obtained from the feed. When applied to aquatic animals, this F.C.R is generally lower than that of land animals, as shown in the table below.
Comparison of common FCR among different species
Its calculation requires the following variables:
- The initial biomass – i.e. the number of fish in a farm population, multiplied by their individual weight — of the production unit under study (pond, cage, pool…);
- The final biomass of the same production unit;
- The amount of feed distributed.
The F.C.R is simple and objective. For these reasons, it is a valuable indicator in the context of fattening farms. It is determined by comparing the initial input of feed (initial amount of feed fed) with the final output of the fish or shrimp that are produced.
The practical limitations of the F.C.R.
Even though the F.C.R. formula is simple, its practical application is much more complex. What other sources of information are available at the farm level in order to provide a more exhaustive idea for the efficiency of a feed?
- Population or sample: should a farmer weigh his entire animal population or just a sample of it? If it is the whole population, the problem is solved. Otherwise, he/she needs to know the exact number of individuals making up that population so the amount of feed needed for calculating the F.C.R can be determined. He/she also has to ensure that the chosen sample is, to a sufficient level, representative of that population.
- Consideration of mortality rate: all mortalities occurring between the date of initial weighing and the date of final weighing are to be deducted from the final biomass. Therefore, their effect on the F.C.R. is negative. Their impact is all the more significant if death occurs late. However, this limiting variable is not so much a problem in the case of livestock management, as only live farm animals can be commercialized.
- Amount of feed distributed: provided that a daily register of activities is held at the farm, this information is usually easy to obtain.
- Actual consumption of feed: from the initial amount of distributed feed, we must find out how much has been consumed.
Other performance indicators related to feed efficiency
When it comes to evaluating the level of performance obtained from a feed, there are other indicators that can complement the F.C.R. A useful indicator for farm management is one that highlights a poor technical result. Its regular application also grants the ability to keep track of the improvements that have resulted from the ensuing corrective actions taken.
- Viscerosomatic index (VSI): the net amount of filet produced should also be monitored closely. A substantial gross weight gain can result from an increase in the mass of viscera; yet, these parts of fish are not as valued as filets. The visceral somatic index (weight of animal viscera / animal weight) can therefore be a very helpful parameter when applied to fish.
- The homogeneity of fish and shrimp outputs is also important. F.C.R. calculations, no matter how objective, can hide significant discrepancies in performance within the same pond.
- The comparison between the various indicators should eventually be carried out methodically. Only the results obtained within similar rearing conditions are relevant: same species, same genetic lineage, even same rationing method, as well as operators and production systems of similar technical levels.
Read Also: When to Feed your Fishes after Stocking
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