The Hatchet

Essay by PaperNerd ContributorCollege, Undergraduate August 2001

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Marine Biology Lab Research Paper Does Density Affect Growth Rate among Fresh water Tilapia? My partners and I started off with a 12-gallon tank, which housed 3 tilapia. We decided that our variable for this lab would be water density. Our tank was kept at a steady temperature of 70 to 74 degrees Fahrenheit. We fed our fish according to their body weight. After figuring out the body percent/ food ratio we determined that it was appropriate to feed them 2.5 grams, and towards the end of the semester 3.0 grams of high protein food.

As a result of our variable we did basic water tests twice a month. These tests consisted of Ammonia PPM , Nitrite PPM, Nitrate PPM, Dissolved Oxygen PPM, temperature degrees Fahrenheit, Salinity %, and PH. After completing these tests we would maintain healthy water by doing a partial water exchange to filter out some of the bacteria/ waste products.

The PH of the tank remained consistent at a 7, except for on October 24 when it was up to an 8. As for the Ammonia PPM remained consistent between .5, and 1. Nitrite PPM and Nitrate PPM, both varied, starting off high, and gradually decreasing as time went on. As for dissolved oxygen it to started off high, and as time went on decreased. Finally, Salinity remained consistent, with 1.006% at the first test on August 20, and 1.006% on the last test November 19.

After comparing results of our tank to others, we determined that depending on what your variable is, that had a big effect on water measurements of all type. For example, a fellow lab group had temperature as their variable, and there temperature ranges were much higher then ours, due to the heater in their tank. When comparing our results to a group, which had food type as a variable, we discovered that a low protein diet had an effect on the PH, with their PH being higher. Ultimately I determined that depending on what our variable is, that will have a big effect on your basic water quality measurements. Every tanks results will differ, depending on how many fish your tank housed, how much food you feed them, how often you do water changes, and just the personal lifestyle of each fish.

In conclusion, our last step is to answer our research question: Does Density affect growth rate among fresh water tilapia? Yes, I carefully determined that it does because we had a substantial growth rate from the beginning of the lab to the end of the lab, which made us believe that density had an effect on the growth rate of the Tilapia.