Some algal blooms are the result of an excess of nutrients (particularly phosphorus and nitrogen) into waters and higher concentrations of these nutrients in water cause increased growth of algae and green plants. As more algae and plants grow, others die. This dead organic matter becomes food for bacteria that decompose it. With more food available, the bacteria increase in number and use up the dissolved oxygen in the water. When the dissolved oxygen content decreases, many fish and aquatic insects cannot survive. This results in a dead area.

No, as you stated above, you had debris because of the air bubbler. You statement explains everything that would have caused you to have a dark tank. You should try to get a filter or change the water while all the crap are on top

No, not directly.

This increase in circulation is good for aerobic nitrifying bacteria that convert nitrogenous waste from ammonia to nitrites. This may however in the short term increase nutrients in the form of nitrates, however changing water will reduce this and also improve your Redox Potential which is also important here. This added circulation will also lower the amount of anaerobic decay and also improve Redox.

What you really need is better filtration in the form of a good such as a pressurized filter, and especially a Veggie Filter (please see this article: http://aquarium-answers. blogspot. com/2007/03/pond-veggie-filters. html ). A UV Sterilizer is also very helpful for Green Water in ponds (although your first step is improving your filtration).

For much more information about Green water in ponds, please read this article: http://www. americanaquariumproducts. com/PondAlgae. html

And for much more over all pond information:
http://www. americanaquariumproducts. com/ClearPond. html

You need plants!! The koi eat, and then create waste. The fish waste combines with decaying leaves to create ammonia, which is toxic to the fish. To counter the ammonia, Mother Nature creates a bacteria called Nitrosomonas that converts it to nitrite. Because nitrite is also toxic, she then creates another bacteria called Nitrobacter that converts it to nitrate (basically fertilizer), which is no longer toxic to fish in small quantities. Plants in the water, including algae, take nourishment from the nitrate, reducing the amount in the water, and rendering the water fish-safe. So, to make it so that algae won’t grow, put more of the kind of plants that you do like in there, so they take up the nutrients in the water that would otherwise be available to the algae.

A general rule of thumb is to have plants equal to about 50% of your pond’s surface. A mixture of potted varieties like cardinal lobelia, water iris, and lillies, plus underwater oxygenators like anacharis, and some floating varieties like water hyacinth, water lettuce, or fairy fern work well.

Some people don’t like to have plants in the actual pond or like to have fewer than the recommended amount, because they like to be able to see their fish better. If this is the case, you can build a separate “veggie filter” and run the water out of your pond, through your mechanical filter(s), and then through a small (roughly 1/4 the size of the surface area of your pond) trough or bog area – lined, and planted with a heavy feeder like iris. You put baffles into the veggie filter to slow down the flow of water, and then from the veggie filter, the water can go right back into your pond. Your mechanical filter will get out all the big particles and the beneficial bacteria will help a lot with the water quality, but the plants in the veggie filter will make the water crystal clear! Here are some links on building a veggie filter: http://www. bonniesplants. com/how_to/vegg. . . http://home-and-garden. webshots. com/albu. . .

Many people build their veggie filter containers up above their ponds, so they can aereate the water as it falls back into the main pond. Others build them more as a bog garden, right into the side of the pond. When we put ours in (just last year, I am ashamed to say), we used a 500 gallon livestock feed/water trough, and cut a spillway into the rim to use as the head of our 6′ waterfall. We have been “ponding” for almost 8 years and resisted putting a veggie filter in – surely, plants couldn’t do as well as all that technology of UV and mechancial filters, right? Wrong! We struggled with maintaining water quality every year until we put one in, and now, our water is crystal clear and clean! In fact, this year, we disconnected our UV and bead filters altogether, and now run SOLELY on our 500 gallon veggie filter (for a 3,000 gallon pond). Our water has never been better, and our fish have never been happier. . . .

Anyway, hope this helps. Good luck!

Try adding some Tilapi to the pond – great algae eaters and there are varieties that tolerate colder water (within reason). They’re actually fun fish and easy to take care of. They also get along well with most other fish. You might look for hybrids as they can be quite prolific.

Good luck

You have to prevent debris from falling into your pond because these are food for the algae. Consider also the ratio of the pond size to the amount of water, number of plants and fish – it must be balanced. And instead of algaecide, put barley straw extracts. It has been proven to have beneficial enzymes which can kill algae. This article also has other preventive measures for pond algae control. Check it out!