Out compete the algae with plants. Make a floating circle out of PVC or anything that will float and contain and toss in water hyacinths. The more the better. They will multiply quickly and then you can sell the babies to me :)
People are using these plants in water treatment facilities. They work as both biological filtration as well as mechanical filtration. Your fish will nibble but probably will not kill them.
If you are in Florida, this may not be possible however as they are considered a noxious weed there.
Here is an article that outlines other plants that can help:

http://www.pondtrademag.com/articles/ar-136/

Check out the pictures of the sweet potato plant.
I am going to try it.

Hi Sully. How old is your pond?
Do you have stones, gravel and or rock at the bottom of your pond?
Do you make water changes from the bottom of the pond?
If so, how much and how often?
Do you have a lot of plants in your pond?

Answering these questions will give me a better idea as to what is going on in your pond.
I used to have a terrible problem with green water in our big pond and in the smaller ponds we had trouble with hair algae.
We got a diagram of a filter from our friend and I've never had a problem with algae since. If anyone is interested, I can send you a copy of the filter.

Your's Koily, Lorraine

Lorraine

The pond is twenty years old and made of cement. It does not leak. There are no stones, rocks, or gravel in the pond.

Water changes are done weekly from the bottom of the pond. Can't estimate the amount but it is only to replace what has evaporated.

I have three water lilies.

Sulli, you didn't say how deep your pond is but I'm not sure that matters too much. I agree with what others have said about adding plants, the more the better. Also, I know most people tell you to add fertilizer monthly, but with your situation I wouldn't do that. The water is too rich the way it is and adding fertilizer will just make it worse.

I'm not quit sure I understand you water change statement. You say you do weekly water changes from the bottom of the pond and then you say you only replace water from evaporation. Replacing water from evaporation is NOT a water change. In fact it is the worst kind of water management you can do. The chemical make up of the water just keeps getting worse as time passes. I would suggest that you remove at least 25% of your water each week and replace with aged water. Another comment is that well water can contribute to an algae problem depending on it's chemical make up.

Just some food for thought. Hope it helps.

I feel like with a working UV filter and a small pond your issue shouldn't be this significant. Are you perhaps running the water through your UV filter too fast? I've read that the effectiveness significantly reduces if the water passes through the UV chamber too rapidly.

Also you might try changing the orientation of your UV filter. If water runs horizontally through the UV chamber and out without filling the space you may not be getting full exposure, if you mount vertically, forcing the pump to fill the UV chamber entirely with water before it overflows into the output pipe, you might get better exposure of the algae to the light.

I had trouble with algae in my ponds for years. I tried the chemicals out there but they were only temporary fixes. Then we got into biological filtratioln and we started making our own. Wow, what a difference. Now our ponds are crystal clear with no hair algae due to the large colonies of good bacteria in our filters which remove the toxins, therefore starving out the algae.

Your's Koily, Lorraine

I use koi clay every year in my pond very little algae. In the spring I put a layer of quilt batting in the top of my settling chamber and it cleans up algae very fast two days. If you don't have a place to put the batting there was a method posted here a couple of years ago that I used when I had a submersible pump. You take a 5 gal bucet and drill holes along the sides near the bottom. Then you pump your water through the bucket. It was a lot harder to control the flow though.....