Two,
Find something to fill up with water to replace all the water in the containers.
Do it one at a time if you have to.
Fill up another big container, let it sit a couple days, and then empty one of your containers and rinse it out good.
THen use the water that you had sitting out, and refill the container, and put the plants back in.
You might want to flush the plants you fertilized with some of the sit out water too, before putting them into the clean water.
Then fill your extra conter up again, and do the same thing for the next container.
I don't fertilize my pond plants at all. They all do just fine.
Someone once said that they fill an extra container with water and fertilize it in the seperate container and then after a day, they put the plant back in pond.
Just an idea anyway.

I have water containers with lotus and waterlilies that are in full sun. The pads shade it pretty good so not too much green in those tubs the one I tried making into a bog gets a lot of green algae in it. I wish I knew what would help. I have tried dumping the water and refilling but it eventually all gets gross again. I have heard that adding copper pennies etc to a bird bath will prevent algae so maybe that would help. I was thinking about putting a piece of copper pipe since its a larger tub than a bird bath. I would have to thread it on a piece of string or something to suspend it in the water so it doesn't fall down into the dirt/mud of the bog....I will post if it works LOL.
One thing that I know controls algae in my chicken waterers is Apple Cider Vinegar. I don't know if it would be too acidic for the plants though. I only have to use about 1/2 tsp in a gallon of water for my chicken waterers.
I have heard that copper might have heavy metal toxicities for animals so I don't use that for my poultry. Not sure how copper would affect plants.

This post was edited by sultry_jasmine_night on Fri, Mar 7, 14 at 12:14

UV filters are 100% effective.

It's not well understood why water sometimes goes green and some times doesn't. It is known that plants give off chemicals that inhibit growth of other plants. For ponds G.P. Fitzgerald in the Journal of Phycology, 1969, showed Pithophora (a common species of string algae) creates a chemical in the water that kills green water algae. In my own experiments I've seen this too and also that green water algae can kill string algae. It's a plant war and the winner is never certain. Norm Meck published an experiment that showed water from a clear pond was toxic to green water algae, kill it on contact, although he guessed the chemical came from bacteria. There are some aquarists doing experiments to see if other submerged plants do this as well. Likely there are since this type of chemical warfare is very common in the plant world.

It's also been demonstrated many times that green ponds almost always test 0 for needed nutrients while clear ponds test high for nutrients. While nutrients can certainly make green ponds even greener nutrients are not directly related to clear water.

If you chase the myth of trying to lower nutrients to get clear water you could just be spinning your wheels. Maybe even hurting the plants that may had been producing the algae killing chemicals.

Emptying water and replacing would only be a short term fix. Normally it produces an even greener pond within a week or two.

There are copper based algaecides. The trick is to get the dose right as it can kill fish and higher plants. Adding copper metal isn't the same thing. Metal releases so few ions that it isn't effective. Copper based algaecides are effective.

These are complex living systems. Impossible to guess what tomorrow will bring. But if you stick with science and stay away from myths you increase your chances imo of getting the results you're after.