For some reason, there are times when a pond has green water and anything you try to clear it simply doesn’t seem to work.
Such was the case with a frustrated small pond owner who corresponded with me over the last few months. Marge is a pond friend who’s kept in close touch as she tried numerous remedies. Products like Algae Fix would work, but only for a few days and then the green water would come back. Add in the mix, barley straw concentrate, bacteria,and more.
Finally we discussed a few “back to basic” things that might help including shading, from plants or physical structure, checking on her pond’s fish load (of which she found she had too many) and feeding routines. But the real clincher was something so simple that most people overlook it.
What could this possibly be you may ask? Water changes. That’s it…just some simple water changes.
Ideally, the only thing Marge could have done differently is to start with partial water changes, reduction of fish, adding some desired plants, or creating some form of shade, rather than hitting it with chemicals right off the bat. But by the same token, we all learn, and evolve our understanding of things via one step at a time. The main thing was that she didn’t give up and wallow in defeat. She kept trying and kept experimenting with things until she found what worked for her pond.
So what’s with the water change thing working here?
The reason I ask is that you very well may have tried to get rid of green pond water by draining and cleaning the pond out completely. Unfortunately this often leads to dismal results. I can’t tell you how many times I’ve heard someone relate this story to me, and end up stating, “but in a week or two the green water was right back!”
And it’s true. Doing a full restart of the pond simply due to a green water problem just isn’t going to work very often at all. The problem with this approach is that, in starting everything over, you’ve taken out any good bacteria that’s starting to get established (you do use beneficial bacteria when you start a pond up right?), and fundamentally, nothing has changed in terms of what caused the green water to begin with. And that’s high nutrient loads and ample sun exposure.
What Marge did was apply partial water changes, consistently over a period of days and weeks. By doing this, she lowered or diluted nutrients such as fish waste, nitrites, nitrates, and phosphates and in effect reduced them. But she didn’t wipe out all the good bacteria that may have become established in her filter, or around the pond.
Within a week or two of turning the water over she started to see clearing. The amount of water exchange will vary from pond to pond but you may find anything from 10 to 50 percent will be necessary to get some kind of effect. Marge is also taking some proactive steps to balance out her fish load, which she admitted was high, and in the process she now has a very clear pond.
I often suggest that people get a good bacteria established and at the earliest possible time they should introduce desired plants that float and provide coverage on the surface. Shading from the sun in any indirect way is also useful. And there’s nothing particularly wrong with using a UV light since these are specifically designed to work on green water.
But somewhere in the early attempts to fix your pond’s green water problem, you may want to do some partial water changes and see if things can clear up for you too!