Why Is Green Water So Hard To Control?

Green water algae, which, as we’ve described before, is made up of millions of single cell algae that freely floats around in a pond, can be very difficult to get rid of once it develops out.

This is not new news for many pond owners that are plagued by it.

Here’s the normal course of events. A frustrated pond owner sees their water turning green. Over a few days or a few weeks time, the appearance could range from just a hint of tint to a full blown green catastrophe where you can’t even see your fish a few inches below the surface.

Quite often there’s a reasonable assumption that since the pond started out pretty clear, if you just drain and change the water out, then maybe the algae won’t come back. But this rarely if ever helps that much. It often turns out that this just ends up as a great waste of time and water because in a short while, the green water will be back, just as it was before.

The problem with the idea that you can just wash this green stuff away is that the root causes of why the algae is growing well to begin with have never been addressed. It’s also important to realize that almost any new pond, or freshly renewed pond that’s being started up in the spring, may very well show some green water symptoms early on.

As I pointed out in this particular video on making your own bio-filter, there is a time early on in a pond’s start up that you should use some form of beneficial bacteria to get some good bugs established in the pond, and in the filter. These are the cleaning and balancing mechanisms that a pond will use to keep things like green water from getting out of hand.

In particular, if you have fish, some type of process will be necessary to convert the fish waste into a non-toxic, plant digestible form, and the key to this conversion is once again, the beneficial microbes. They, in essence, neutralize nitrites, and ammonia, (two lethal substances in ponds) and covert them into nitrates which can be consumed by other bacteria and plants.

Now you may be thinking, but wait, algae is a plant, so why would I want to make this stuff available for algae? Well, you don’t really, but the problem is, if you don’t convert these things, they’ll eventually build up and kill fish. By the same token you can probably see that if you happen to have too many fish in a pond for it’s size, and the biological processes or your filter system is overwhelmed, then green water is a much better result, rather than having a high ammonia level. So yes indeed, in a round about way, that algae is helping to keep things in check somewhat.

I’m not saying that you should want it, or like it…that’s just how things are in the real pond world. Normally green water isn’t hurting anything except maybe the appearance of your pond, and your hopes and dreams of clear water. Some people learn to live with a little bit of it…and I think that’s fine if you’re only dealing with a light tint. If it get’s denser however, most people want to do something about it, and fortunately there are some basic things that can help.

These little single cell algae are like any plant. To get it to grow you’ll need two things. Some decent nutrients it can feed on, and sunlight. We can tackle each one of these things directly and many times, reduce algae in the process.

Step #1 – Nutrient Control

To work on the nutrients, I’ll often make sure my beneficial bacteria counts are high and sustained. If it’s early on in the start up process, I’ll remain patient and not treat the green water directly, and simply wait until my bio filter and bacteria counts are built up. Normally in 4 to 6 weeks you’ll see the water clear when things come into balance. Be sure as well to leave the bio filter alone as much as possible. You can clean the prefilter screens if you have them but don’t disturb the bio-chamber where the home and media is for the colonizing bacteria.

Even if the bottle or package of bacteria suggests treating once with the stuff at the start of the season, I’ll normally advise that folks routinely add this maybe once a week or every other week until the pond starts to clear up. This may simply help to speed the balancing process up just a little bit, although you don’t have to go overboard with the bacteria. Steady and consistent will win the race often enough, although there are times when you may want to double the suggested dose for your pond size, just to make sure you’re not underdosing with the stuff.

Step #2 – Sun And Shade

The other part of the “secret” to controlling green water is to take the sun into consideration. Nine times out of ten, if a pond has green water issues, it’s also getting more than ample sunlight exposure throughout the day. Ponds that have a bit of shade often stay clearer, and there have been many instances where ponds with green water issues see improvement if some kind of shading is provided. In the past we’ve discussed all kinds of things including physical barriers. Shade sails, umbrellas, pergolas, you name it, it’s probably been used.

In some cases, pond dye can help, and I’ll use this in larger ponds where there’s just no way to provide physical shading. And I should note here that even though big ponds don’t have filters, we still usually like to use bacteria to clear things up if possible.

For small, or backyard fish ponds, above all these things, I’ll always prefer desired plants. Lilies that float and spread across the surface are absolutely the best way to provide shading and they also provide additional nutrient absorption where they can outcompete algae and thereby help to keep it in check.

The vast majority of the time, if you use bacteria and plants, along with good fish population management, you can keep green water under control. And it’s all done naturally.

Final Tips On Green Water Control

Beyond these basic strategies, I would be remiss to suggest that you won’t ever need to do anything else where green water is concerned. There are times when it becomes chronic, or you just can’t adequately address some of the things we talked about above.

So now what’s a pond owner to do?

There are still options so take heart. UV light is my first choice for small ponds, when it comes to direct control of green water. They were designed for that, and if necessary you can easily install one in your pond’s flow system. This video talks more about how UV works and how to get it set up right in your pond.

For large waters, ultrasonic algae control systems may work well. I emphasize the word “may” because they are very effective when the algae type is right, but there are a few (maybe a handful of algae) that can be hard to control due to their cellular structure. Often it’s worth doing an algae test to identify them.

And finally, in some cases, the prudent use of algaecides may be helpful. Note how I’ve saved these for last, because in my opinion, that’s where they belong. But for smaller ponds, Algae Fix is one type of algaecide that has worked on some green water issues. Many people ask me about the peroxide cleaners such as Green Clean and Algae Off, but I don’t really recommend them for green water. I’ll do a future post to explain why…just trust me on this for now.

For larger waters, (but not for small ponds) I often suggest the use of Earthtec which is a low dose copper algaecide that can help with green water and still be safe for fish.

Oh, and when it comes to string algae problems, I have some more good news. Most of what I’ve talked about in this article, other than UV light, will also work, or help with filamentous algae problems too. So try a few of the basic things first and you just might find that after a simple change here or there, your pond will start looking a lot clearer.