Annex B - Data from Research


Why Lettuce?
Lettuce Hydroponics is the culture of plants in a soilless medium. It is a common plant used in hydroponic systems. It is a hardy plant that has a fast growth rate. Lettuce is the first salad crop to be cultivated commercially, worldwide. 

Butterhead Lettuce
It is known to be the most heat tolerant and bolt resistant among all the lettuce types. (Ly, 2012) It has a loose forming crown, with a silky texture to the lettuce leafs. It is known for its sweet flavor and tender texture and goes well with any type of meal. There is moderate amount of vitamin C. It takes around 50 to 70 days to mature. 

Hydroponics System
The water used has to be around 6 to 7 pH. The temperature of the water has to be around 21 to 25 degrees celsius. The lettuce will bolt (flower) in temperatures above 27, which is not desired as it slows down the rate of growth. 

Nitrifying bacteria takes place better at pH lower than 7.5. Removal of ammonia can be done by denitrifying bacteria. Ammonium is oxidised to nitrate (No2). Nitrites (No2) will then be converted to Nitrates (No3). Denitrification increases pH of the water.  

Tilapia fishes are under the cichlids family. They live in water around pH 5-10 and temperatures of 24 to 28 degrees celsius. They live in brackish water, of 5-10 ppm, which is also categorised  as fresh water. They are bottom feeders and requires food that sink to the bottom. The dissolved oxygen level has to be above 5 mg/L, nitrate levels must be below 5 mg/L, ammonia levels must be below 3 mg/L. Ammonia levels should rise up to very high around 1 to 5 hours after feeding.  

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