KOI and warming winter days in the Lowcountry

KOI and warming winter days in the Lowcountry

Hello Charleston KOI keepers

Hello all in the greater Charleston, S.C. Metro area, otherwise known as the Lowcountry.  We have a lot of advantages living in this area, to include the weather. These conditions can make for a great environment to grow Koi.  But this also can make us a little lazy especially in the winter time.

Today we are going to talk about dealing with our swings in weather.  We can go from 60 to 30 and back to 70 all in the same week.

We will talk about why Warm weather is more dangerous to your fish than cold temperatures, during the winter.

Warm weather is more dangerous to your fish than cold temperatures, during the winter.

For those of you living in the Lowcountry, this time of year might bring about some periods of cold and warm weather.  For example, we have had a few days of freezing colds already this season along with days back up in the 70’s. Some of you might think this is great news! The ponds will warm up and your fish may even start perking up and swimming around.  A few warm days will do them good right? That is so WRONG.

Cold and warm weather pose a huge threat to your Koi for reasons that we will explain.

Problem One: Ammonia.

Ammonia, the toxic chemical produced by the fish and by decaying material in your pond, is normally processed by the nitrifying bacteria in your biofilter and converted into less toxic chemicals.  However, in winter the cold causes this biofiltration to stop by killing some of the nitrifying bacteria and forcing the rest to go dormant. Whether you run your filter or not, your biofilter doesn’t remove the ammonia in winter (at least not as fast as summer to really make a difference).  While many people might test their pond’s ammonia levels diligently in summer, very few of us Koi-keepers continue to test their water in winter. This is usually not a problem because even though it’s not being removed as it normally would in summer, ammonia is much less toxic to your fish at lower temperatures.  In fact, in water below 45 degrees F, ammonia is harmless to your fish. So even if there is ammonia in your pond in winter (and there usually is since your biofilter’s not removing it), as long as the water’s cold enough, it can’t hurt your fish. My pond for example rarely goes below 50 degrees F. Last year when the Charleston area had the ice storm my pond went down to just below 40 degrees F.

Water temperature above 45, any ammonia present in the pond can be toxic. Ammonia reading of .25 ppm won’t hurt your fish if the water temp is below 45, but it will stress your fish more and more as the water warms up.

Another problem is that during warm spells, your fish become more active and produce more ammonia.  Their bodies respond to the warmth by speeding up their metabolisms slightly: they start “breathing” more rapidly, and their digestion systems start moving a little faster.  Like the fish, the bacteria in the pond also become more active and some start feeding on any organics in the pond. All of these processes increase ammonia production.

Our ponds in this area normally stay warm enough that ammonia is toxic even in the winter for our fish, but more of it is being produced in the pond, and almost none is being removed by the dormant or reduced activity of the  biofilter! This becomes a Triple threat.

In short: if the water temp in your pond is above 45, YOU NEED TO TEST YOUR WATER.  Test like you would in summer: for ammonia, nitrite, and kH, and fix any of these that are an issue (ammonia and nitrite should be 0, your kH should be at least 140 ppm) just like you would in summer.  If your ammonia and nitrite are zero and your kH is at least 140 ppm, you can sit back and relax for the time being. Just keep testing regularly if the water temp is above 45.

Problem Two: Bad bugs can be active most of the winter here.

Like your fish, any parasites or pathogens that were dormant in your pond during the cold will become active when the water warms.  This is why it’s important to perform a fall cleanout of your whole pond whenever possible. Dirt and muck harbor parasites. If you don’t get rid of the muck before winter, those bugs go dormant with the fish until the weather warms again.  Then as soon as warm weather hits, they “wake up” and attack your fish.

Parasite problems are much harder to deal with in winter because many treatments don’t work at low temperatures.  In fact, the only option for treating parasites in winter (without removing the fish from the pond, bringing them inside, and treating them in a holding tank) is to bring the salt level up to .3% (or sometimes higher) and hope for the best.

Problem Three: Your fish are already cold stressed.

During winter, your fish’s immune systems are reduced along with all their other metabolic processes.  They’re conserving energy for basic bodily functions: keeping the gills, heart, and brain working in the cold.  This means they’re weak and vulnerable to any additional sources of stress, like poor water quality and parasites/pathogens.  In this weakened state, they can’t adapt to any additional stress, so suddenly certain factors that wouldn’t affect them very much in summer can be dangerous in winter.


During winter warm snaps your fish are weak when the bad bugs are strong and when water quality (specifically ammonia) could be dangerous.  During these periods, you need to watch your water quality and your fish. When we have warm days, you need to test your water and keep an eye out for any abnormal behaviors.  This last part is very tricky because the fish are still so sluggish from the cold. If you detect ammonia and your water temp is above 45, (which could be most of the winter here) you need to detoxify until the ammonia drops to a safe level (0).  If you observe nitrite, add salt just like you would in summer. If your kH is below 140ppm (100 ppm at the very least), add the appropriate amount of baking soda just like you would in summer. If you start seeing evidence of parasites or pathogens: wounds, white fuzz, fish flashing or laying over, or hanging/ gasping at the surface, immediately bring the salt in the pond up to .3%.

All these things are meant to reduce any and all external stress on the fish, since they’re weak from the cold, and any additional stress could easily push them over the edge and kill them.

It’s easy for Lowcountry Koi owners to get complacent in winter, but don’t let your guard down.  Your diligence is the only thing that will save your fish.

String Algae in Your Pond

Are you dealing with a String algae invasion? Here are some suggestions to help keep the algae under control.


What is String Algae?

String algae is a filamentous species that attach to plants, hangs from rocks in waterfalls, or hangs on the surface of the water. The long strands tangle together and form thick mats that can double their weight within 24 hours!


This mess can attach rocks and is not to be confused with the good algae that grow on the side of the pond. String algae are ugly, but not a major danger to your fish’s health.

A large amount string algae will reduce oxygen content, but doesn’t mean your water is bad. It is a sign of beneficial water qualities. Somes algae are acceptable since it contains a beneficial variety of carpet algae which is home to important micro-organisms that fully promote a healthy water column


How To Remove String Algae from Your Pond

To remove and reduce string algae you must scoop it out first and then get to the bottom of the issue in your water chemistry if it comes back.

Your waterfall will be the most difficult place to remove algae in your pond. Since the water rushes by so quickly it is difficult for water treatments to do their job effectively. To completely rid your waterfall of string algae it may take up to 2 seasons, so be patient and make sure you are not adding too many nutrients that encourage algae growth!


Steps for String Algae Removal & Reduction

  1. Physically Remove String Algae – This is your best method for removing string algae. Though it may seem dirty, it is essential to do so you can reduce the amount of decay. Pull the biggest bits of string algae near the base. Physical removal is the fastest way to get algae out of your pond. The hand approach is easiest. Wearing gloves is not required but may keep you cleaner. Use a long-handled brush to pull out the algae at depth.


  1. Treat Water and Kill Off Remaining Algae – Some people suggest using a pond algaecide to kill off the remaining algae but we do not recommend chemicals. You’ve worked hard to make a natural oasis. In the springtime, the good bacteria levels can be low. We recommend adding bacteria/enzymes to assist the natural process. Normal green hair-like or carpet/blanket algae which grow on pond walls and some rocks are best left untouched and completely acceptable.


  1. Add Extra Plants and Remove Decay –  Place quick growing and reproducing plants in your pond to increase oxygen content. Make sure you take out the decaying plants first, as they will not help your fight against algae. Choose plants that will grow larger, consume a lot of nutrients, and will not require a lot of upkeep. We recommend Water Lettuce, Irises, and Cattails for the spring and summer. Make sure you remove some of your extra plants from time to time to let new growth occur in your pond. You can solve many problems as a pond owner by placing plants to out-compete algae and suspend algae for excess nutrients. Just be careful to not add in any plants that already have string algae attached!


  1. Find the Cause of the Algae Growth – Look for potential causes of string algae by testing your water quality. If algae are growing at a problematic level than it is time to look beyond the algae and mat and deeper into the pond chemistry. High pH and Phosphorous levels are the leading cause of string algae. Examples of what can cause high pH are the clearing of algae blooms, excessive plant growth, overstocking of fish, and the introduction of foreign materials (untreated concrete, rocks containing limestone or calcium/granite). The most common cause of high phosphorous is from fertilizers that have leaked into the pond water. Iron is also a major contributor as well as grass clippings that find their way into the pond after mowing the lawn. Scoop green grass blades out immediately.


  1. Feed Koi & Fish Less to Reduce Excess Nutrients – One of the most common errors by fish pond owners is to overfeed their fish, thus adding excess nutrient to the water. If there is any food left in the pond uneaten, you’ve fed your fish too much.  By feeding less you also increase the fishes’ appetite for other substances in the pond. Like algae! Try feeding your fish less this summer and see how fast they will cut through a string algae mess. A few corbicula clams in the pond is a way to keep excess nutrients cleaned up and in check. Each clam filters up to a half a gallons of water per hour.


Should I Use Barley Straw and How Much?

Barley straw is a great organic product to use, but it doesn’t exactly kill existing algae. Barley creates conditions that prevent the new growth of algae. Put it in your pond early as it can potentially create a temporary algae bloom later in the season. Be careful, overdosing the pond with barley straw may cause fish kills, due to the straw de-oxygenating the water as it decays. Also, make sure you know where the barley comes from. Some farmers spray the barley fields to kill bugs.  These can still be on the barley straw and kill your fish.

2 lbs per 1000 gal of water are the recommended amount to use. In still and small pond waters the dosage of straw should be 2 oz per square yard of water surface area. When it is applied to cold water (less than 50°F), it may take six to eight weeks for the straw to begin producing the active chemicals that reduce algae. In warmer water above 70F, it becomes effective in as little as two weeks. In any case, barley straw remains effective for approximately six months after it is applied. If the straw starts to smell, it should be removed and replaced.


A Few Other Tips to Control Algae in Your Pond


1. Remove Leftover Decomposing Algae

Breaking down some of that excess organic matter is critical to controlling algae long term. Many ponds have from 3 to 24 inches of organic matter resting on the bottom. This organic matter releases excess nutrients as it decomposes and more so if the pond has a shortage of oxygen in its deeper parts. A more radical solution to removing the excessive organic matter is dredging or even draining the pond, cleaning out the bottom and starting over. This can definitely work but is very expensive. Also, once you clean out the pond, the problems can start all over again unless you take a proactive approach to managing excessive organic matter.

2. Add Extra Aeration

Adding aeration and circulation in your pond is the most important thing you can do to help prevent algae long term. Aeration increases the level of dissolved oxygen in the bottom part of the pond which increases the number of aerobic bacteria. These bacteria, in turn, begin to feed on the excess organic matter and reduce the number of nutrients released.

3. Add Beneficial Bacteria

Beneficial bacteria work at the decomposing excess organic matter, sticks, leaves, decayed fish and excess nutrients. They don’t have to be combined with aeration, but adding oxygen will significantly increase both their numbers and their level of activity at the bottom of your pond where you need them most.

4. Scoop and Remove Algae with a Rake/Eradicator

Another commonly used option for algae control is manually scraping with a rake or weed eradicator. These options are not for everyone and can require considerable time and effort to be effective.

5. Block the Sun

Is your pond getting direct Sunlight? One way to slow the growth of algae is to provide some shading for your pond.  This can give you time to let some of the other attempts to work.


Enjoy your Pond

Lowcountry Koi Club.