Glass or plexiglass under water will quickly, as in 2-3 weeks, start to develop an attached periphyton film that can get 1/4" to 1" thick. Depending on the water quality of the pond and the algae flora present both will have a big effect on what grows on the underwater glass surface. As an example of what type of periphyton your pond will 'produce' look closely at some of the underwater surfaces in your pond. You an also put a clear glass jar or similar thing under water and monitor its appearance over the spring, summer, fall, winter. This will give you a good idea of how often you would need to clean your observation 'bubble'. Keep in mind that your line of sight underwater in your specific pond will be the same or less than the secchi disk reading.
Last edited by Bill Cody; 01/23/17 10:32 AM.
