How To Tell If Your Beneficial Pond Bacteria Is Depleted

Beneficial bacteria for ponds is impossible to see with the naked eye. These little good bugs do a lot to help keep a pond cleaner and clearer, and we owe a lot of thanks to Mother Nature for giving us the head’s up on just what these microbes can do.

In ponds that are naturally clear, it’s a pretty good bet that good bacteria is playing it’s part in the equation. Without it, the pond bottom will accumulate stuff to the point where you’ll end up with a lot of muck or sludge, and water quality problems, like algae, will start to develop out.

But beyond the obvious issues that come from poor bacterial performance, we often get the question…”How can I tell if my pond bacteria is depleted?” It’s a good one to ask, but a bit tougher to answer, but I’ll try to do justice to the question below. Namely, I want to discuss how pond bacteria can be damaged, diminished, or wiped out due to some simple pond management mistakes.

In all man-made ponds and particularly those you’ll find in the backyard, it’s long been suggested to add some beneficial bacteria to the water once a pond is started up. This goes for new installations and for upstart ponds that are coming off a long winter season of little to no activity.

Because many koi ponds are kind of unnatural in how they’re put together, and due to the possible influence of fish waste build up, the use of good bacteria isn’t a bad idea throughout the season. If one has a biofilter then that can do a lot of the cleaning and balancing work, but even with those, you’ll often need to prime the filter with good bugs anytime the water flow through the device is shut down for very long.

So apart from the basic start up advice above, the other main consideration for the pond owner is to consider ways to support bacterial work, and maybe even more importantly, how not to hinder or hurt it while working with your pond.

Keep in mind these are living, breathing little microbes and while they tend to be hardy little buggers, they can be damaged by a couple of different things.

For small ponds I’ve found that the top three impactful things that can negatively affect bacteria include UV sterilizers, water chemistry, and chemical algaecides.

Ultraviolet Light

Let’s start with Ultra Violet light. As you probably know, or should be aware of, UV is very targeted to dealing with green water algae. You can learn more about how UV works here.

The key to remember though is that UV is indiscriminate in what it will damage. It can damage and kill single cell algae of course, and it can kill certain pathogens which is usually a good thing. But it can also damage good bacteria too.

So, if you have a UV running, and decide to add bacteria, be sure to turn the light off for 24 to 48 hours while the bacteria circulates through your filter, and pond unimpeded. After a time you can turn the UV on again if you like, but I have often advised that you may also want to leave it off longer if your not having issues with green water…at the least you may save on bulb life and give your bacteria a chance to thrive.

Water Chemistry

Water chemistry doesn’t really have to be complex when it comes to pond bacteria. You do however want to know what your pond’s pH, alkalinity, and water hardness might be.

Most commercial bacteria will work in pH ranges from about 6.7 to 8.5 with little problem. The closer this number is to neutral (7.0) the better. Alkalinity should ideally be between 120 to 180 ppm, and total hardness should be between 75 to 150 ppm. Inexpensive test strips for ponds or aquariums can be used to test for these things. (note: pool test strips often don’t have wide enough ranges or readings to be much good in ponds).

Algaecides And Chemicals

Not all chemical algaecides are necessarily bad for bacteria. However anything containing copper has the potential to kill a lot of good bacteria and this includes the bacteria that sets up in the pond itself but also it’s reasonable to assume that since this copper can build up in a biofilter, it will likely damage or kill good bacteria in there too.

Ideally copper based products should not be used in small ponds, and particularly those with fish. Pond ionizers have become more popular in recent years and these sort of time release copper into the water. They can definitely restrict algae growth and will be useful for that, however it may not help much to add good bacteria to the water with the hope that this will keep the bottom of the pond cleaner or more balanced. It would be best to go with one or the other for the best and most cost effective results.

Now it would be an injustice to leave out another important component regarding beneficial bacteria and it’s performance, and so we really need to look at the role that aeration plays here too. Since good bacteria is aerobic, it requires decent oxygen levels in the water to perform well. Low oxygen can be an issue in smaller ponds for sure, but I’ve found it most often in large waters with ample depth.

What About Large Ponds?

When it comes to larger waters, everything I mentioned above still applies, other than the UV lighting of course.

Pond aeration while not an absolute necessity can be a game changer when it comes to using bacteria. As ponds get deeper, the levels of dissolved oxygen often go down, yet the cleaning bacteria do a lot of the work at bottom cleaning, and they require good oxygen to keep up. This is why subsurface aeration may turn an algae laden pond around, all by itself from time to time, and without it, supplemented bacteria may still lag and not restore a pond to a better condition.

Water chemistry needs to be decent, and most often it will be, but this can vary around the country. In certain areas that have a lot of limestone in their ground, then pH can be high, so it’s worth checking to find out.

And finally, copper algaecides and certain herbicides can be very detrimental to good bacteria. Many ponds have been treated over the years with such products and if your pond is one of them, it’s highly likely that most of the microbes will have been knocked down and out through repeated use of these chemical cocktails.

This doesn’t necessarily mean that you shouldn’t ever use such things, but it’s unrealistic to think that the natural cleaning processes of a pond won’t be affected as a result.

In cases where a herbicide might be used for an aquatic weed problem, once the treatment is applied and the growth successfully controlled, then after a few weeks it’s not a bad idea to follow up with some supplemental bacteria just to build the stock up again.

The Bottom Line On Bacteria

When all is said and done, there is no one thing that will work exactly the same in every pond or in every case. However it could be said that if you’re able to maintain, protect, or supplement a sustained level of good microbes into a pond it will improve it’s health and appearance more often than not.

There are things you can do to support this work, and things that may be done to hinder it. And it’s ok to go either way as long as you know what you’re getting into and how to correct certain imbalances if they end up coming about.

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