Help! 1/2 acre pond in SE Indiana. My electric aerator is in the shop but my windmill has kept an open area 8 yards ice free. Today I spotted a very thin layer of yellow/green film-like algae(?). Is there some type of chemical control I might use now without harming the fish (heavily stocked)and waterlilies, and would work at cold temps. For the last couple of summers this algae film would appear and I used a hand pool skimmer and constant aeration to control it, but always felt like it was about to explode if I turned my back. The Koi are now quite large, the bass are well fed with shiners and minnows twice a year plus existing blue gill. I have been trying to catch and remove some substantial size channel cats for the last 3 years. I have never used any chemicals.
Any Ideas?

machdog, The slight sign of algae is a sign of a healthy pond.I would continue to remove it in the spring if you want it out of your pond once it floats to the top.If you can continue to be "chemical" free" I aplaud your effort, the entire ecosystem of your pond will thank you for years to come.Your windmill aeration for this winter is more than enough. Chances are the algae you see are producing plenty of DO. Any chemistry in your cold waters would be futile at this point.Be more concerned if you dont see any algae in the winter as DO can be difficult to maintain under snow covered ice without it.Also keep in mind that aeration is only going to "reduce" the nutrients that algae thrive on.Your pond will always need nutrients to support a proper enviroment for your fish.Good Luck Ted

As your pond ages it does annually accumulate more stuff that includes or results in nutrients. Always remember it is a pond with living things, not a pool. PONDS GRADUALLY OVER TIME BECOME MORE NUTRIENT RICH TO GROW MORE PLANTS; natures law. Rates of accumulation vary with each pond bassed on its design. Thus expect to see a little or a lot more algae or plnat type growth each year depending on nutrient inputs.

As your lily or weed beds enlarge they can if abundant enough in late spring and mid summer absorb most of the nutrients that algae would utilize for growth. Early spring when rooted plants have not "taken off" in growth for the seasson cold water filamentous algae can get a head start in the pond. The more algae that you can remove early in the year allows the plants to catch up on nutrient absorption as the season progresses . However plants will be able to take up only a certain amount of nutrients and algae will greow on any excess nutrients. In some marginally enriched ponds the rooted plants can absorb enough nutrients to keep filamentous algae amounts reduced/ suppressed all summer and fall.

I recommend you stay away fro chemical control as long as your back and algae removal net hold up. A better algae removal net than a pool skimmer is a long handled smelt diping net 3/16"-1/4" mesh (Cabelas is one source) .

I am happy to report that I feel much better after reading the replies to my algae problem. The last 24hr it has been windier so the windmill is pumping more and the water does look better. Thanks so much for your help.