A lazy (and frugal) man's pond -
I have been trying to find a way to have a low cost but sustainable pond, and finally found one. Filtration is out because of the frequent requirement of maintenance. It turns out this can be done with less than $150.
What's the solution? Fine Bubble
Help to break down algae-forming nutrients - Decomposing bacteria is needed to break down the nutrients that cause algae growth. Namely, aerobic (oxygen breathing) bacteria. Aerobic bacteria is extremely efficient. The oxygen supplied by a fine bubble aeration system allows this bacteria to perform important tasks in the water column. One of these tasks is the essential breakdown of algae-forming nutrients, such as nitrogen and phosphorous. Without ample oxygen in the water, this rate of breakdown becomes much slower and algae begins to overtake the surface of the water. This can lead to eutrophic waters, and an overall collapse of the pond ecosystem. http://en.wikipedia.org/wiki/Water_aeration
Get rid of unpleasant pond odor - When there is not enough oxygen present in the water, aerobic bacteria become dormant. At this point, anaerobic (non-oxygen breathing) bacteria takes over. Not only is this bacteria up to 20x slower in terms of nutrient breakdown, but it also emits byproducts such as methane and hydrogen sulfide into the atmosphere. This is why you are often met with an odorous stench when walking by a stagnant pond. The mere presence of oxygen is enough to reduce this problem.
Some fine bubble aeration kits cost a fortune. I found one diffuser with base that costs less than $66, the Ceramic Dome Fine Bubble Diffuser, ABS Plastic Base. Beyond that all you need is an air pump and a tube. You can get an air pump on eBay for less than $50, plus another $30 for a self-sinking air tube. The total comes to less than $150, and doesn't require weekly maintenance.
According to Agriculture and Agri-Food Canada, "small diaphragm compressors work best for dugout aeration because they perform well at the pressure ranges (up to 15 to 20 psi) needed to aerate dugouts. An air compressor of 1/4 to 1/8 hp putting out about 1 cubic foot per minute (cfm) is sufficient to aerate a dugout up to 5 million litres (1 million gallons)." See http://www4.agr.gc.ca/AAFC-AAC/display-afficher.do?id=1187622591044&lang=eng