Found this cool article wrote by someone else.



I have goldfish. I know the trendy thing is koi, but I have goldfish. When I'm trying to sound uptown, I say they're shubunkins, and who knows, they might be. I don't carp on it. One is more round than long with fins like Sally Rand's fans and a couple are white with orange spots.

When I first put in my lily puddle, I had koi, because I thought I was supposed to. But koi are rowdy, constantly attacking water plants and keeping the bottom muck roiled up. As one by one they floated to the light, I replaced them with goldfish. I mean shubunkins. They have better manners. If you think you must have koi, keep in mind that koi will not sleep on the foot of your bed or respond to their name. Neither will goldfish, but goldfish are cheaper. For several years I had three fish. I figured they must be all males or all females, who can tell. Then two years ago I got babies, and this year more. I probably have too many fish for my lily puddle, but the older ones are not quite big enough to filet yet.

The story is that too many fish make green water, and they often do. The reason is simple organic chemistry, not the kind we forgot from high school, but the kind we have learned in the garden. Fish eat and excrete … you know, nitrogen. Fertilizer. With lots of nitrogen in the water and summer sun, algae thrive. Green water.

But my water is clear enough to count the bottle caps on the bottom, even read the brand. No filter of any kind. And the reason is, as in many things in life, balance. I wish I could apply that maxim to my bad habits as easily as I do with my pool.

If your pond turns green, you have either too many fish or not enough plants, but probably the latter. Or maybe not the right kind of plants. While you want fish with good manners, you don't necessarily want plants that behave. Many plants grow at a gentlemanly rate and use modest amounts of nitrogen, but some are gluttons.

My favorite, and the one to which I attribute success in … uh, fertilizer mitigation, is Acorus gramineus 'Variegatus' or striped ribbon grass. Looking more like an iris than a grass, if it were a blind date it could be described as a great personality and not hard on the eyes. It's winter hardy up north here, fairly attractive if not quite drop dead gorgeous, the root mass provides a good spawning mat as well as a place for the shy fry to hide. But its best feature is a humongous appetite, and if there is more nitrogen than it can consume, it grows enough to suck up more.

Another nitrogen glutton is water hyacinth. It has a couple of advantages and one disadvantage. For one thing, you don't have to plant it. Just throw it in the pool. It floats. Given warm water and enough food, water hyacinths will multiply rapidly, even covering the entire surface, depriving the algae not only of nitrogen but of sunlight. Of course that also deprives you of watching the fish, which is why you put fish in there in the first place, not just to feed the plants you put in to absorb the fish output. But the excess is easy to haul out and it makes good compost.

The one disadvantage is that it isn't hardy. You need to buy it new each spring. Given the way it multiplies, it should cost about a nickel a clump, but you know it won't.

Sometimes duckweed works. It has some of the same advantages as water hyacinth, but there is a different kind of balance problem. Fish eat it. If it is happy and multiplies faster than the fish munch, you're in business. If not, it disappears or dwindles to a few tiny specks hiding in safe places.

Here's the point. If you have a green water problem, don't spend $100 to $1,000 on a filter system. Spend $10 on plants.

http://www.dailylocal.com/articles/2011/07/24/life/srv0000012654407.txt?viewmode=fullstory

Sorry Kory the story is not totally truthful. Green water has a great deal to do with sunlight.

Mmmmmmmmmmmmm