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09-25-2003, 12:04 PM
Hi all,
Since such questions as - How many fish per tank? and How fast will they grow? - come up in this section time and time again, I've found this tid bit of info that might help some of our new memebers.
Growth rate, or the rate of change in fish weight, is affected by factors such as:
* amount of food (if amount of food is low then growth is slow)
* type of food (if food does not have adequate protein fish will grow slowly)
* oxygen level (if oxygen is low growth may slow down)
* water quality (if compounds like ammonia are high growth will slow down;
* if pH and salinity are high the growth will slow down)
* temperature (if temperature is low growth will slow down)
* type of fish (some species grow faster than others)
* sex of fish (males grow faster than females)
* size of fish (small fish grow faster than bigger fish)
* social factors (if fish are too crowded growth will slow down)
* stress (if fish are stressed growth will slow down).
The simplest way to monitor growth is to follow the rate of change in weight of fish over time. That is, if the rate at which the average weight of fish is monitored over time then the effects of the factors listed above on growth can be determined. The simplest method of calculating growth rate is percent average daily growth. This is calculated as:
[W2 - W1/W1 (t2 - t1)] x 100
where w2 = weight at the end of the observation period, w1 = weight at the start of the observation period, (t2 - t1) = the length of the observation period in days. For example, if the average weight at the start of a 30 day observation period was 80gm and the weight at the end of the period was 120gm the percent average daily growth rate would be:
[120 - 80/80(30)] x 100 = 1.67% per day.
Since such questions as - How many fish per tank? and How fast will they grow? - come up in this section time and time again, I've found this tid bit of info that might help some of our new memebers.
Growth rate, or the rate of change in fish weight, is affected by factors such as:
* amount of food (if amount of food is low then growth is slow)
* type of food (if food does not have adequate protein fish will grow slowly)
* oxygen level (if oxygen is low growth may slow down)
* water quality (if compounds like ammonia are high growth will slow down;
* if pH and salinity are high the growth will slow down)
* temperature (if temperature is low growth will slow down)
* type of fish (some species grow faster than others)
* sex of fish (males grow faster than females)
* size of fish (small fish grow faster than bigger fish)
* social factors (if fish are too crowded growth will slow down)
* stress (if fish are stressed growth will slow down).
The simplest way to monitor growth is to follow the rate of change in weight of fish over time. That is, if the rate at which the average weight of fish is monitored over time then the effects of the factors listed above on growth can be determined. The simplest method of calculating growth rate is percent average daily growth. This is calculated as:
[W2 - W1/W1 (t2 - t1)] x 100
where w2 = weight at the end of the observation period, w1 = weight at the start of the observation period, (t2 - t1) = the length of the observation period in days. For example, if the average weight at the start of a 30 day observation period was 80gm and the weight at the end of the period was 120gm the percent average daily growth rate would be:
[120 - 80/80(30)] x 100 = 1.67% per day.