Q & A Of The Day

Why Aren’t My Fish Eating?

A common question we get in the fall or winter months, and this is particularly from new pond owners…but they wonder why their fish stopped eating as the weather cooled down.

And the answer, is very simple. Many fish simply go into a type of dormancy in cold weather…their digestion slows way down as does the transport of food through their digestive system. So you really want to stop feeding your fish once the water temps drop down to about 50 degrees…at that point feeding your fish regularly could be problematic for them.

What’s Better, A Pond Aerator Or A Pond Heater?

by Mark

Tammy from Iowa wrote to us recently and asked, “We have a small pond, maybe 800-900 gallons. Is it possible to have to strong of a bubbler going? We have about 15 fish and its about 40 inches deep in one spot. We live in Iowa and it will be soon be freezing. Just wondering if too much bubbling can hurt the fish?”

Answer: Tammy thanks for the question! I like to use a small aerator in garden ponds during the winter months, but I would suggest either providing a way to float the air stone or diffuser off the bottom and near the surface of the water, or moving it over to an end of the pond, or even a shelf if you have one. I mention this because you have 4 feet of water depth which is very good. It’s deep enough to allow the fish to go to the bottom and settle there when the weather get’s really cold. The water may be a bit warmer there, and ideally you don’t want to disturb that water, but only keep a bit of the surface agitated.

Unlike the important use of aeration during hot weather, which is a time when oxygen can get low in pond water, in the winter you don’t generally run into that problem so the main benefit of an aerator is to keep a spot of ice open when things freeze up.

Since we’re on the topic of small ponds and winter freeze ups, let me note here that most experts suggest having at least two feet of depth in a pond in order to overwinter fish safely. If there’s any doubt about your ability to winter fish in safety, then it’s probably better to just create an indoor holding tank that’s warmer, well aerated, and filtered adequately.

Pond Heaters And DeIcers

The other option, which can be used together with an aerator, or totally on it’s own is a small pond heater. Most of these are designed to float or be kept at the surface and they’ll do a pretty good job of keeping the ice open even in really cold weather. A few models have detachable floats that keep them near the surface, but they also can be placed at the bottom of the pond to keep more of the water warmer. In most cases, the most important part of this work is really to keep the surface open so that any gases, and things that build up in the water can be released and not trapped under the ice.

Ideally I think in the coldest of conditions, a pond heater is a better choice than an aerator. These are generally pretty affordable and all you need to do is plug them in. It needs to be kept in mind that they won’t simply turn on once they power up. Many of these heaters come with a thermostat built into them so that they only come up, and use power, when the water may start to freeze up. Above that temperature they’ll remain turned off.

In Iowa we can get a few periods of some really cold weather, such as in January and early February. If you know some really cold stuff is coming along, then I would have the heater in place and use it as needed. If you want to run an aerator near the surface when the temps aren’t so brutal there’s nothing wrong with that at all.

Once the weather begins to warm up again, you can eventually move the air stone from the surface, or a shallow area, and back into the deeper part of the pond when the summer comes along. In other words, we want to aerate the entire pond during the summer, and only a small part of it during the winter. So bubbles won’t bother the fish at all if you set things up right based on the seasonal needs.

Should I Run My Aerator In The Winter?

by Mark

Tom from Wisconsin, a traditionally cold state in the winter time, wrote in and asked if it’s a good idea to use a pond aerator even in the cold months of winter? In addition, his pond is very shallow (around 4 feet deep and about 1/3 of an acre in size) so the particular aerator that would be used might be a bit different than a typical farm pond.

Answer: Tom, thank you for your timely question and it’s one that many people wonder about. The base answer is yes, it’s a good idea to aerate a pond all year round.

Many people know the value of aeration during the hotter summer months, and sometimes they end up learning the hard way that oxygen can get depleted in very warm weather and they lose a large number of big fish as a result. However it’s also a good idea to use aeration if you live in cold weather climates.

Winter Pond Aeration

Cold water aeration isn’t quite as much for maintaining oxygen but to keep an area that’s open from ice. If the pond surface is covered for an extended period of time, and particularly if the pond bottom has some organic build up, or a heavy fish load, some toxic gases can build up and get trapped in the pond, to the potential detriment of any fish.

If an ice hole is maintained, then these gases can be released into the environment and fresh oxygen can be brought in so this is an ideal transfer that keeps a pond and it’s inhabitants a good bit healthier.

Aerators are a good choice for this work because they are generally pretty cheap to operate and if you get a good quality system it should provide years of dependable service. Pond aerators tend to be very discreet in how they operate. They don’t shoot a column of water into the air, but release very fine bubbles into the water, at the bottom of the pond, and these rise up in a column and agitate the surface area just a bit to keep ice from forming.

Shallow Pond Aerators

So with the basics of winter aeration out of the way, let’s discuss more specifically the best type of system for your particular pond Tom.

Over the years a typical pond aerator would have a single compressor that sits on the shore and an airline that runs to a diffuser that sits on the bottom of the pond. Usually if a pond has something like 10 feet of depth or so, you can expect this single diffuser to work well in a pond up to about 1 acre in size. The compressors are usually around 1/4 horsepower. Then as ponds get bigger, you’ll see the compressor get a bit more powerful and additional diffusers will be used to cover the increased area.

This changes though in a shallower pond. Ponds of say 6 to 8 feet or less don’t benefit as much from a single diffuser package. The area this single release point of air would help is diminished somewhat. In other words, the deeper the pond, the more area a single release point will help with.

So the answer to this is to use some smaller diffusers, and usually a bit smaller compressor (stronger compression isn’t as necessary in shallow water) and spread the release points of air out a bit more. Something like a 1/2 acre size pond that’s 6 feet deep might have four small diffusers working in it, rather than one large one. And the coverage and total aeration will be much better with the specially designed system.

Using Shallow Pond Aeration Kits In The Winter

The final part of this answer is fairly important because we want to make sure we keep that spot of ice open in the water. This is less likely to be achieved if we keep the diffusers spread out a great deal, such as we would in the warmer months. So my suggestion is to move these diffusers into a tighter pattern in order to concentrate the agitation caused by the released air at the surface. This is particularly important when you run into really cold weather such as you’ll often seen in northern states like Wisconsin.

In the end, the tighter you make the pattern of released air, the colder the conditions it should be able to help with. In climates that have more moderate conditions, the diffusers could either be spaced a bit wider just as a precaution to any icing that might occur.

Simply put, pond aeration is one of the most powerful tools that a pond owner can use to keep a pond in a better looking and healthier condition. And although you don’t have to do so, using it year round can be very helpful to maintaining fish health and vitality, no matter what season you’re in.

Here’s a helpful video from our sister site at Pond Algae Solutions that discusses shallow pond aeration in more detail.

I Have A UV Light In My Pond But Still Have Green Water

by Mark

John writes, “I have a 1500 gallon backyard pond and have installed a uv light in it which was supposed to help with green water problems. It doesn’t seem to be helping very much, and I wondered if I did something wrong?”

Answer: Hi John and thanks for the question. Your plan to use a uv sterilizer in your pond to combat green water is a good idea. In truth, when you hear companies talk about fighting pond algae problems with a uv filter, it’s single cell, or green water algae that they are talking about specifically.

In contrast, string algae won’t be affected because it can’t pass through the tube and be exposed to the ultra violet light, which does all of the damage. In the case of green water, this discoloration can vary in a pond and the degree of just how green and dense it will get is totally dependent on how many little, single cell algae you have growing in the pond. These can expand in number quickly when conditions are right so a pond can be pretty clear or lightly tinted one day and totally green the next.

A pond uv light basically irradiates these little critters and will either damage or kill them and in doing so, it makes them clump together in a larger mass which is more easily filtered out of the water by a good quality pond filter. What’s interesting is that individually, these single cell algae can be so small that they’ll pass right through many filter systems.

Which brings me to an important point. A UV system is not the only required component in a small pond’s filtration system. Ideally they should be paired with a good biofilter which actually captures and breaks down these dead or damaged algae cells. UV will do nothing to reduce nitrites, nitrates, or other material which can be broadly classified as nutrients coming from fish waste, among other things. Only a biofilter will help with these so it’s important to include this in the mix.

Green Water Continues

Interestingly, many people who have UV light installed in their ponds may still have problems with green water. This usually indicates that something will need to be adjusted to get this to work better. Most manufacturers have ratings for how much water flow should run through the uv over a period of time. For example, a very common rate would be the full gallon volume of the pond should circulate through the uv and filter system once every hour. This insures that the water and algae cells are passing in front of the uv light frequently enough to be affected.

It’s best to follow the product maker’s suggestions but if you need to, it may also be useful to slow the water flow rate down a little bit if you’re still having problems. A slower pass rate may help expose the algae to the light a bit longer and this can make a difference in performance. Normally some type of restriction valve can be put inline and help with this flow rate control.

You may find that some uv lights come with several suggest flow settings. A higher or faster rate would allow the unit to work as a clarifier, which means it may control algae, but not decimate things like beneficial bacteria so much. UV is indiscriminate in what it will kill or control…good bugs, bad microbes, viruses, and algae are all targeted.

On the other side of the flow rate coin, a slower flow rate will provide a sterilizer effect on the water. A more thorough eradication of all affected elements will be made because of the longer exposure time to the ultra violet light. Either rate, or somewhere in between will likely create the best results for your pond in terms of algae control. In an ideal setting, you would want more a clarifier effect but this may not be possible for every pond.

Another reason why uv light may not be getting the job done is that the uv bulb will need to be replaced from time to time. Many people assume that because it’s still lighting up that it’s working fine but this isn’t always the case. Most bulbs have a operational life where they will provide ample ultra violet radiation and then begin to drop off in terms of performance. Twelve to fourteen months of operational life is common. After that you’ll likely want to replace them for improved performance.

And finally, if you’re in the market for a uv light or considering it for your pond, it’s important to make sure you get one that’s rated for your pond’s gallon size. A pond owner really shouldn’t scrimp on any of the important mechanical components in a pond, such as the pump or filter system. UV light is no different. Remember that to work well, the full gallon volume of the pond should probably pass through the uv pond filter at least once per hour, all day long.

With a bit of troubleshooting and detective work, you can get better performance out of your pond uv light and in doing so, you should be able to control green water algae without the use of chemical algaecides.

Can I Use Pool Products In My Pond?

by Mark

Janine wrote in recently with a very common question. She asked, “Can I use swimming pool products in my pond?” She went on to mention that she’s had some algae problems in her pond and had tried chlorine for a time but wondered if something else might help the situation.

Answer: Thanks for the question Janine! I’m glad you asked because you are surely not the only person wondering about this. Here’s my take on this topic. I have always taken a very conservative approach to treating my pond or water garden. Which basically means that in a general sense I don’t ever suggest using a pool product in a pond.

You obviously don’t have fish, if you’ve used chlorine in the pond, or at least I hope you don’t. Chlorine and fish simply don’t mix well, and the same could be said for many pool related chemicals. They might work well in a swimming pool but would probably cause major issues for fish.

Some testing tools like pH strips may be useful but even with these, many pool strips don’t test in a wide enough range to be of use for pond owners. Ideally pH test strips should run from at least 6.0 to 9.0 and higher to be of much use.

Finally let’s talk a little bit about the filters used in each setting. Bead filters for ponds and swimming pool filters look very similar on the outside but that’s about as far as the similarities go. If you looked inside you’ll see many differences. The piping and tubes that route the water flow will probably be different and more than anything else the media inside will vary too.

Swimming pool filters normally will contain sand, and this is a great substance for filtering out chemicals, oils, and small debris that might enter a pool. In contrast, a pond filter usually has a biological component, or in other words, there is an active area in the filter that provides a home for beneficial bacteria which can help break down organic wastes such as ammonia, nitrites and nitrates, found in pond water. Physical filtration will also take place in a pond filter but the biological elements are the most important function of the filter.

Many pool filters that have been tried in ponds end up clogging up quite a bit and water quality problems can still be an issue because the organic elements aren’t being filtered out very well. One could try to change out the filter media in a conversion attempt but normally it’s just easier and simpler to purchase a good quality filter that’s designed for pond use and you’ll end up getting better results.

Pond And Lake Restoration

by Mark

What happens when a pond get’s “old and is dying”? What can be done to save it or restore it back to what it once was?

Todays Q & A comes to us from Janet that sent us a link to an interesting article from Sag Harbor News. It seems that Mill Pond, an old and well established lake in the NE United States is in very bad shape. You can read more about this unfortunate situation through this news report.

Answer: Thank you for the link and for your question Janet. It’s inevitable that every pond will age and unfortunately part of that process is a natural “filling in” of the pond basin with all kinds of things. Sediment, blown in debris, shore erosion, the growth and die-off of plants like algae and aquatic weeds, organic material like leaves…they all add up to a pond that is in a state of degradation.

As I’ve often told many large pond owners, the number one goal that you have is to slow this filling in down as much as possible. Some of this may come from proper design considerations but even with this, nature will run it’s course.

Organic build up at the bottom will eventually lead to very high nutrient loading in the water, and like any decaying material, it will serve to create a nutrient density (high phosphates are one component) that is sure to help other aquatic plants grow prolifically. Nutrient spikes can also come from run off from highly fertilized ground around the pond. Algae blooms are fed by these things, and as algae is killed or dies off, it too will add to the organic build up. Nature has a way of dealing this mucky build up, namely naturally occurring beneficial bacteria. But if conditions don’t exist for this to be optimized, then the biological activity simply can’t keep up and the pond keeps filling in at an accelerated rate.

I personally don’t know the history, or the size of Mill Pond but in most cases, you would want to optimize the restoration capabilities of the pond itself. Dissolved oxygen levels should be checked at various points in the pond to make sure they are adequate to support aerobic bacteria. This is particularly important near the bottom where oxygen levels are normally lower. If the readings show a deficiency then some form of bottom based aeration should be installed to improve the condition if it’s feasible to do so.

Along with that, you’ll find that mineral supplementation was mentioned. Interestingly, if a pond has very soft water with low mineral content, and in particular low calcium levels, the natural bacteria will not have the raw material needed to bind to the phosphates and neutralize them.

If algae is a continual problem, chemicals should not be used to control it. Most algaecides contain some level of copper which although it’s toxic to algae, it’s also detrimental to good bacteria, and this is essential to maintain as it’s really the most powerful pond restoration device that’s available. For immediate, non-chemical algae control, it might be possible to limit it’s growth with the bacteria and aeration alone, however if more help is needed, new technology like ultrasound may also be useful to test out.

As the article states, this approach has never been a quick fix to a problem that has developed over many years, however it is the best hope for the pond to be restored to a healthier condition. The good news is that if the proper resources are available and some consistency is applied in the management of the pond, there is ample evidence that the pond can be afforded a new life as a cleaner and clearer body of water.