I will take fish food with that warm water

Despite what the calendar says, it’s time for the fish to wake up.   They are waking up on their own, and they are hungry.  Watching the Koi is a good indicator that it might be getting close to the time to start feeding them a low protein food again, but really, its not like the fish stop shivering or put up a sign saying “Feed me!!!”.

I use water temperature as the final guide.  Over the holidays, you may remember I got one of these nifty remote temperature gauges, so I can plan out my Koi Garden days from the warmth of my house.  Nice....  Once the temperature starts getting higher than 50 degrees F, for extended periods of time, the fish will be able to digest the food they eat.  The fish’s immune system also turns on by that time and helps the fish fight the waking bad bacteria and diseases.   The increasing temperatures also allow the beneficial bacteria of the filters to start the Nitrogen cycle.

With all this happening, it is a risky time for the fish, plus I have not even mentioned my personal war with the Raccoon, but again I digress.  In a normal spring, the temperature gradually increases over 50, with multiple dips back into the 40s and even 30s.  I think this stresses the fish and increases the risk of sickness.  Therefore, in the Koi Garden, I try to reduce the risk with the help of an aquarium thermometer which is placed in the external filter assembly.  This has heated the water flowing from the filter to the pond and reduced the fluctuations in the water temperature, especially when the temperature drops below 50 degrees F. 

The heater should also allow the beneficial bacteria to take root and begin to do their job cleaning the water at the earliest possible time.  At the same time, I have also turned off the UV sterilizing filter, to make sure the beneficial bacteria have a fighting chance.  At this time, I am going to put up with green water if it means the filters get started correctly.  Better to have a healthy Koi that I cannot see due to green water than an unhealthy Koi clearly visible in the bottom of the pond…..

Testing the water chemicals during this timeframe is very important as things can change within days.  In the Koi Garden the Ammonia and Nitrite levels have not been too high yet, but if they do rise above safe levels, water changes may be necessary.  I will keep my eyes on this in the future.

A chill is in the air….

Well the summer is gone, at least for now.

This drop in temperature affects the inhabitants of the Koi Garden Pond as much as it does humans. While we can scurry for the fall sweaters and sweatshirts, the Koi cannot do so. Even though a large percentage of the Koi Garden pond is situated underground, which moderates any temperature changes, the water still does change according the air temperature. I just checked the water temperature today and it has gotten down to 58 degrees F. It was in the 70s a week or so ago.

There are two parts of temperature change to be concerned about: The resultant temperature; and the speed in which the temperature changes.

Now the 50s are not really a problem for the Koi. You can continue to feed the Koi, just switch the food to a lower protein variety. As we mentioned in earlier blogs, temperatures less than 50 degrees are where you have to be more concerned. That is when I stop feeding altogether. So imagine the problem if/when the temperature raises over 50 again? Do you start feeding again? Continue not feeding? And what about the food previously eaten but not fully digested? All sorts of problems can and do occur. It is better to go through the temperature change through the 50s just once or twice a season.

So, back to our old friend, the aquarium heater. We use the heater to regulate the pond and filter water temperature. It won’t keep the pond above 50 degrees all winter, but it will slow the decline. And that is really what we need to do anyway.

Much better than trying to fit a sweatshirt on a Koi...

Ammonia is for cleaning, not Koi ponds.

Every week or less I perform water tests on the Koi Garden pond. This test includes three basic tests. Depending on the results of those tests, I might do some additional more extensive testing. I normally do testing with chemical droplets applied to a sample taken from the pond. Depending on the test, up to two different sets of drops may need to be applied along with a regimen of mixing and waiting. The resultant mixture is color compared to key cards included in the tests. Based on the color key, some action may be required: change of water, addition of some chemicals, etc. I am also trying a new type of test I found at Lowes (Lowes.com). It is a strip of paper with the testing mediums for all the tests painted on the each paper. The paper is dipped in the pond water and then reviewed against a key for color changes. The strips include tests for Nitrate and Nitrite, including pH and water hardness. Despite the absence of a direct Ammonia test on these strips, the convenience alone makes them desirable. In the tests I performed, the strips appeared to get the same results as the chemical drops.


Based on these most recent tests, I got some responses that required an action. But before we discuss the failed test, some background is required. The key to the biological filter is the nitrogen cycle. See below for a figure of the nitrogen cycle (diagram below). Ammonia results from the decomposing Koi waste and any other biological matter that gathers and decays in the pond. Beneficial bacteria called Nitrosomonas converts the Ammonia into Nitrites. Nitrites are converted to Nitrates by a different bacteria called Nitrobacter. Additional beneficial bacteria ingest Nitrates to fully clean the water. Knowledge of this nitrogen cycle and the correct interpretation of the test results allow a person to respond correctly to clean your pond.



When I applied this series of tests to the Koi Garden pond, I got an indication of higher levels of Ammonia than were warranted. In new ponds and ponds at the beginning of the warmer season, it is common to see some Ammonia responses on tests. These indications should reduce or go away fairly quickly as the beneficial bacteria grow. It may take up to 4-6 weeks to get all the beneficial bacteria growing in your filters. In my last tests, I had very low Ammonia, and progressively higher Nitrites and Nitrates. This indicates that the biological filter was “moving through the Nitrate cycle”. To have the Ammonia levels increase rather than decrease indicates that the amount of the particular beneficial bacteria was decreasing rather than increasing or remaining stable.

There are two actions that must be taken:
One, immediately reduce the level of Ammonia in the Koi Garden pond; Two, remove the cause of the increase of Ammonia levels.
1) The best way to quickly remove the Ammonia from the pond is partial water changes. Change 20 to 30% of the pond water and replace it with clean water. The addition of salt to the pond water and having a ph outside the range of 6.8-7.5 can both reduce the toxicity of the Ammonia. Salt should not exceed .2% in a pond but in a bath can go to .3%.
2) Removing the cause of the increased Ammonia is a more complex issue. There could be a number of causes for increased Ammonia. A rapid increase in food, sunlight, an increase in degrading biomass in the pond, an increase in the number of Koi in the pond, and a decrease in the number of beneficial bacteria are all possible causes for increases in Ammonia. In the Koi Garden pond, no additional fish or increased food amounts were introduced. I did not think the amount of leaves in the base of the pond were significant enough for the Ammonia I was measuring. I may have inadvertently increased the dead material as an outgrowth of killing the algae. In a future blog, I will write up discussions about adding plants to a pool and also a tool that works as a great cleaning device.

In previous blog entries I had discussed the green water or algae we had in the pond। To counter the algae, I turned the UV filter on. In a few days the green water was gone. The UV light sterilizes any live organic material in the water so it would have killed the algae and it would have dropped to the pond floor or end up in the filter where it would have acted like any other dead organic material. Pond hygiene is a solution to this problem. This could have added to the Ammonia in the pond. The UV filter might have caused the Ammonia situation to be worse in another way as well. The UV light will not only sterilize algae but it will also sterilize beneficial bacteria suspended in the water. Most of the time, beneficial bacteria introduced into a pond will eventually find a home in the filter medium or attach itself to the pond wall. But newly introduced bacteria will remain suspended in the water for a while and will, if it passes through the UV filter, get sterilized by the UV light. If I had not waited enough time after introduction of beneficial bacteria to the time when I turned the UV filter on, I could have reduced the amount of beneficial bacteria. The solution to this would be to turn off the UV filter whenever I introduce beneficial bacteria to the pond.

It's all becoming clear to me

Last week the Koi Garden pond was a thick and dark pea soup. It was difficult to see the fish at the surface much less when they were submerged near the bottom of the pond.

I then turned on the UV filter.
The UV filter does not work in minutes but it does work.

UV filter setup
The water is pulled into the system via a submersible pump at the far end of the pond. It pulls water through a smaller filter assembly. This filter stops leaves and debris from entering but also has enough filter medium to allow for some biological filtering to take place. The water is then split up into two paths. One path goes directly to the larger biological filter outside the pond. The other path goes through the UV filter and then is returned to the pond via a Venturi tube.

This setup has a number of benefits.

First it allows for some water to reach the exterior filter WITHOUT going through the UV filter. This means that some water will not encounter the UV light and its sterilizing capabilities. This is good. Remember, there is beneficial bacteria suspended in the water that you don’t want to diminish, and the UV light’s sterilizing capabilities does have a negative effect on that bacteria in addition to the algae that makes up the pea soup.

Second, by splitting the water paths, it has the effect of slowing down the water that goes through either filter. This allows the UV light and it’s sterilizing effects more of a chance to have an effect on the water. It allows the UV light more time to sterilize the algae suspended in the water. In the other path, it also allows the water going through the biological filter more time to come in contact with the beneficial bacteria and clear the water.

So after being turned on for 4 or 5 days the water clears up quite nicely. The algae which causes the green water is killed via the sterilizing power of the UV filter. Make sure you test the water both before and after using the UV filter. The algae will feed on the ammonia produced by the fish waste. The UV light will also kill beneficial bacteria as well as the algae. So while the UV filters clear the water up to cristal clear levels, they also might cause increases in the ammonia levels, and therefore Nitrate and Nitrite levels as well.

Pea Soup anyone?

Every spring it comes. And every spring we come up with more tools to fight it. That green, algae filled water that restricts us from seeing the beautiful fish we pamper so much.

I have a nice UV light that will sterilize the water and keep the single cell algae in check very well. The UV light is positioned in the pond in between the in pool filter and the large exterior filter. The UV light is positioned so that only half of the water going to the filter goes through the UV filter, the rest goes directly to the exterior filter. This setup guarantees that the UV light will not sterilize all the water and kill all the bacteria in the water and the filters.

I do not have the filter on all year. I leave the UV light off for the winter and the beginning of the spring. I didn’t want to do anything to reduce the amount of beneficial bacteria in the water until the bacteria filters are up and running. I don’t mind green water for the beginning of the warmer season.

Green water in itself is not an indication of a problem. It could just be that your biological filter is not functioning yet. It is however, very important that you check the water often. You should check for Ammonia, Nitrates and Nitrites. It is also important to check the water PH level; it should be between 7 and 8. Also make sure that the Oxygen levels of the water are high. If you have lowered your waterfalls for the winter, it is time to increase the flow and oxygenation. I think that you should also turn on any Venturi tubes you may have in your pond to get the frothy Oxygen flows.

If any of the measurements are too high, you should remove 1/4 or 1/3 of the water and replace it with new water. Please note that if you do use salt, check and adjust your salt amount after you make any additions of new water.

Wake me up in the Spring

As the temperature rises over 40 degrees, the fish begin to wake up and move around. I wait until the temperature gets over 45 consistently before I start feeding the fish. I then turn the filter heater on, if it isn't already. Having the heater on tends to even out the fluctuations in water temperature from day to night. This year we have had many days where it dropped down to near freezing. In fact, on April 1st we had snow for about 4 hours during the day. Not the typical spring we're used to in Seattle. But the filter heater keeps things fairly even.


The other thing using a filter heater does, is it allows the bacteria that will reside in the filter a chance to grow earlier. This year I introduced bacteria capsules into the central water entrance of the filter April 1st. The central water entrance is also where the heater assembly is located so it provides a nice environment for the bacteria to grow. These bacteria tablets are available at most pond stores. (I purchased mine at the neighborhood Lowes.) I also spent some time performing water tests for Ammonia, Nitrites, and also Nitrates. If any of those get too high, I pump ¼ of the water out (onto the lawn) and replace it with new water from the tap. I try and check the water every week, maybe more often as you are trying to establish your filters.