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From: Gordon J. Mengel
Time: 11:40:37 AM
Remote Name: 188.8.131.52
Plants (e.g., algae) need sunlight and nutrients to grow. Tanks used to grow fish that are located in greenhouses or outdoors can provide an optimal environment for algae growth. In ponds, algae growth can be controlled 1) mechanically by removal, 2) chemically (copper sulfate, potassium permangenate), or biologically by growing organisms that feed on algae. Of course, the method that is used depends on the type of algae that is causing the problem and what treatments are allowable. People that raise fish in home aquaria learn quickly that if the tank is exposed to direct sunlight a lot of time will be spent cleaning algae off the sides. By locating the aquaria away from direct sunlight, using a flourescent bulb for lighting, and by adding fish such as "algae eaters" or snails the tank will stay a lot cleaner. If your tanks can only be located in your greenhouse, then you might try shading the tanks from direct sunlight. Of course, you'll want to remove the algae that has already established itself first. Depending on what type of algae it is and how well established the algae is, you're only real options are to physically remove the algae by scraping the sides of all tanks and pipes or draining the whole system and cleaning everything and starting over again. Finally, I'm sure you've recognised that your situation provides some interesting opportunities for student investigations. Since you have 2 systems, your thought about maintaining one in the greenhouse (as is) and one in an area without direct sunlight (e.g., classroom)? What about trying a comparison between trout and a second species (preferably an algae eating species) or raising more than one species in polyculture? Have the students identified the algae that have colonized your tanks? Do they know anything about algae and algae culture as a form of aquaculture? The mini-system was designed to allow teachers and, in particular, students to do just these sorts of investigations without all the costs of larger systems. Hope you'll find something here that helps.