Koi Rescue
Phoenix Arizona

Koi Pond Regular Weekly Maintenance

Water Changes

The most important thing you should do with your pond, is to remove atlease 15% of the water in the pond every week and replace it with new fresh water. Doing this solves many problems, and dramatically increases your water quality, and let your koi's immune system keep them healthy. Real koi kichi (koi nuts) change 15% of the water every day.

Evaporation is a big issue here in Arizona. As water evaporates, it leaves behind minerals in the water, so if you only "top off" the water, what happens is the minerals build up and screw up the water quality. Keep in mind that koi came from rivers, which are continually supplied with fresh rain water.

Another side benefit is that koi produce a natural hormone that prevents the growth of koi. This is a natural defense mechanism so incase a bunch of koi are stuck in a small pond in the wild, they don't outgrow their habitat. So regular water changes will help dissapate that hormone, and speed up growth.

Tips For Water Changing

For draining the water, most people have ponds in the ground and often will use their main filter pump to partially drain their pond water. The problem is it takes a long time, gets boring waiting for the water to drain, and sometimes gets forgotten and whoops... come back and the whole pond is drained.

I discovered a technique that works pretty well. Setup a special pump on an electrical timer that is used only for changing water. This pump is not fully submerged, it is only deep enough in the pond that if the pump is accidentally stuck on, it will only drain down to the 15% level. Better to let the pump run dry, than to kill all your fish. And most pumps have a thermal cutoff, so if you do let it run too long it will overheat and shut off itself, and then be able to run again after it has cooled off.

For filling your pond, it takes forever with a garden hose and if you forget and leave it running & change too much water, you will shock your fish and kill them. For instance, my 3000 gallon tank takes about 50 minutes to refill the 15% regular water change. I have tried just about every mechanical crank timer on the market and they all fail after a while, usually they stick in the on position.

The solution I use is I setup a regular lawn irrigation timer and solenoid valve (sprinkler system timer). I don't use the auto timer part, just the manual run for X number of minutes feature. The picture to the right is my setup, because I have a bunch of quarantine tanks, I made a pvc T tree and a hand valve / hose that runs to each tank.

Filling Your Pond - Use A Sprinkler Head

Tap water has clorine in it, and koi naturally investigate waterfalls (and streams of water) so if you fill your pond with a hose, the koi will swim right up to the hose and start breathing water that has a concentration of chlorine in it. This may burn their gills and cause damage. To fix this problem, setup a sprayer or sprinkler head on the end of your hose so it sprays the water around your pond as it fills it. Not only does the spraying aerate the water to help dissapate the chlorine, but it also dilutes it quickly with pond water so the resulting concentration that the koi breathe is very low in chlorine.

PH and Baking Soda / Oyster Shell (chicken grit)

An ideal PH for koi ponds is around 7.6 to 8.2. Ponds built from concrete and with a large amount of rocks in the system tend to keep their PH balanced just fine. Ponds which have a plastic liner and all plastic parts tend to have problems keeping their PH at an acceptable level. If your pond PH drops below 7.6, then you should add baking soda to increase the PH. Add 1 cup per thousand gallons, per day until the PH is back up to the proper level. A better, longer lasting solution is to add some crushed oyster shell which will slowly dissolve and buffer your water, so it will keep a stable PH. Crushed oyster shell is commonly sold as "chicken grit" at local feed stores, about $10 for 50 lbs. Just put some chicken grit in a net bag, and put it in your pond near water that is flowing.

Filter Flushing & Cleaning

You should flush your filter atleast once per week. The good bacteria in filters aerobic, and the newer colonies perform the nitrate conversion process at a much faster rate than old colonies of bacteria, so by flushing the filter you get rid of the anaerobic muck, and also sluff off the old colonies of bacteria, so new ones can form. I have a home made barrel filter that I installed a knife valve in, so for me it is as simple as turn off the pump, open the valve and stir with a stick. Whatever filter you have, configure it so that it is easy to do, so you will do it more often.

Full pond clean out - WARNINING - you can kill all of your fish!

Good filter designs collect water and debris from the bottom of the pond so you never build up a muck layer. However many ponds I have seen in people's back yards are not configured that way, and they have layers of muck, leaves and debris. That muck layer builds up over time, and then occasionally owners do a big "clean out". This is very dangerous and can kill all of your fish in just a few minutes.

What is happening is that that muck layer creates an anaerobic environment which harbors toxic bacteria and substances. If you disturb this area while the fish are in the pond, it will release those toxins in the water and kill the fish. So if you want to perform a big "clean out", you should remove all the fish to a temporary holding tank and then perform your clean. After the clean out, get the pond running again for atleast 3 days, and then you can start to replace your fish a few at a time.

My pond water is clear, doesn't that mean it is healty water?

No. Clarity has nothing to do with the quality of the water. Ammonia, nitrite, and nitrate are all toxic to koi. You can have perfectly clear water, and kill your fish, or significantly stunt their growth. To see what levels you have, you need to test your water with test kits. If your filter is operating properly, you should have almost no ammonia and no nitrite. The nitrate is the least toxic to koi, and it will build up in a pond. The only way to get rid of nitrate is water changes or a signifiant supply of plants. But just becuase you have plans, that doesn't mean you can skip the water changes - you need to do those regardless of plant load.


Koi can be pigs and consume mass amounts of food, and on the other hand they can survive on small amounts of food. The more you feed, the bigger they will grow, but keep in mind that you need a filter that is big enough to handle the amount of food you feed. Koi can survive and be healthy on as little as 0.5% feed rate, per day. On the other hand, owners looking to get maximum growth are known to feed up to 3% feed rate per day. If you feed less than 0.5%, then the koi start to become stressed, and start having health issues.

The way to calculate your feed rate (the amount of food you feed), simply calculating the body weight of the koi you have, and figuring the dry weight of the food you feed. So if you have 29 lbs of koi (464 ounces of koi), then a 1% feed rate is 4.64 ounces of koi pellets per day.

Koi and goldfish to not have somachs, they just have a long intestine. This means it is better for them to graze on food all day long instead of just one big feeding per day. So you should split the food and do multiple feeds per day. A common feeding schedule is to give them some food first thing in the morning when you wake up, then some right after you get home from work, and the rest right before you goto bed. If you can split it into 5 feedings per day, they can process the food much better - and this helps them grow faster.

NOTE: If you find uneaten food in your pond, then something is wrong. Either you are feeding too much, or you have water quality problems, or your filter isn't big enough, or something else. Also see below about the temperature to stop feeding.

How To Calculate The Weight Of Your Fish

The simplest method I have found is to make estimations based on the length of the fish. What you do is place something in your pond that you know the length of, such as a decoration or even just a stick. As the fish swim past the item, you can see how long they are compared to that item. You can even take photos as they go past, so you can look at the pictures to help with the comparisons.

You then make a list of all the fish you have, and how long they are. Now that you have their lengths, you can use the following average lengths to figure how much they weigh. This may seem complicated or laborsom, but you really only need to do it once or twice a year.

Typical Weight of Standard Fin Koi, Per Their Length
(the length includes tail fin)
4"     0.62 oz
5"     1.21 oz
6"     2.09 oz
7"     3.33 oz
8"     4.96 oz
9"     7.07 oz
10"     9 oz
11"     12 oz
12"     16 oz
13"     20 oz
14"     26 oz
15"     30 oz
16"     40 oz
17"     45 oz
18"     56 oz
19"     66 oz
20"     77 oz
21"     82 oz
22"     102 oz
23"     120 oz
24"     134 oz
25"     150 oz
26"     160 oz
27"     180 oz
28"     210 oz
29"     230 oz
30"     150 oz

How To Calculate The Dry Weight Of Your Food

First you need to figure what container and scoop works best for you. I personally use a peanut butter jar and it's lid as the measuring cup, however many people use a big plastic jar and a real kitchen type measuring scoop. Whatever measuring scoop you use, put 10 scoops of food into a container and measure it with a postal scale. Then take that weight and divide by 10, and you have a pretty accurate weight of one scoop your food. Write that on the scoop, so you know how many scoops your fish need. For an example, I found that my peanut butter jar lid holds 1.75 oz of my pellet food.

Homemade Koi Food

I have seen large healthy koi that were fed regular koi pellets PLUS large amounts of table scraps. I have become convinced that feeding your koi fresh foods is essential, because processed & dried foods seem to destroy the nutritional value of the ingredients. There are lots of recipies on the internet of how to make your own koi food.

For the food I make, I take koi pellets and run them thru my blender dry, this makes a powder. I set that aside, then blend up a bunch of vegetables to make what looks like a milkshake. I then mix that by hand with the powder, plus wheat germ, wheat flour, corn meal, and other random stuff to thicken it up. I split that up into portions that are the right size for 1 week of feeding. Then I move one portion to the refrigerator, and pull off chunks daily to feed to my koi. Not very scientific, but my fish like it. Also I feed cooked shrimp, and cooked tilapia.

When it comes down to it, Koi are basically river carp, and river carp are garbage eaters that scavenge anything they can. So I figure the more variety I feed my koi, the more of a natural diet they are getting.

Cold Water - Winter Break - No Feeding

A koi's metabolism is mostly based on the temperature. At temperatures between 60 and 87, you should feed the full daily amount. At temps between 56 and 60, you should cut the feed rate down to 0.75% or less. After the water temp drops to 52 and below (and stays down there), you should stop feeding until the temp rises back above 52 and stays there or above.

The koi go into a slow state and mostly sit on the bottom of the pond during this cold time, and they don't process the food very well. This is a normal part of their yearly cycle, they build up a lot of fat in the fall to carry them through the winter. Your filter will mostly die off also, so in the spring when you start to feed again, feed lightly for a while to build the bacteria up again.

Hot temperatures -- reduce feeding

One of the problems we have in Arizona is the water temperature can rise very high, I have seen temps as high as 96 in my tanks. One summer, the water stayed at 96 for about a month and a half. The koi reduce the amount they eat when the temp gets above 88, so if you notice this, then cut back on the amount you feed.