What are my koi doing?

[David Demarest]

Our pond is about 15’x8’ and probably 3-3.5’ at its deepest point. In the pond, we have three fairly large koi, a large catfish, a small sunfish, and a four month old koi that beat the odds and is now part of the pack. We never saw any of his other siblings, which we thought was kind of odd. There’s a story in my head behind his appearance, but that’s another topic entirely. I created this post because I’ve seen the koi doing something odd on a couple occasions.

When I feed the fish, I unplug our waterfall for about 2-3 hours (they take their time when eating), and plug it back in after. I fed them late today (around 7:15pm), so when I went outside at around 10:30pm, the three large koi were all grouped around the filter box. One eventually swam towards the middle of the pond, but two stayed put. It looked like one (the large orange butterfly koi) was trying to suck off some algae from a rock, but the other just seemed to be...gasping? Is that what’s going on? I live in New Jersey and it’s been 85-95° every day lately, which I believe makes the oxygen in the water deplete faster, but it’s a pretty big pond in my opinion.

Can most of the oxygen deplete that quickly? If that is the case, what kind of solutions should I look into? More plants in the water? Less time with the waterfall unplugged? If you don’t think that’s the issue, what do you think is going on? The catfish, baby koi and sunny never do this. It’s just the three big koi and it’s not every day. I did feed them twice today, so maybe the waterfall was unplugged too long (remember, each feeding session is 2-3 hrs of no waterfall).

I took several videos (one has my pale white hand in it for size reference and so you can see how close I could get to them) and uploaded them to Dropbox. The link will be at the end of this post, let me know if it doesn’t work. I’ll post some screenshots from the videos here. Hopefully you guys have an idea what’s going on and the solution isn’t going to cost a fortune!

https://www.dropbox.com/sh/kj8jbguxvfe6is5/AAAUN1RpZcTaknSYbsjCWoV_a?dl=0

 

[Lisak1]

Hi @David Demarest !

Several thoughts:
If it takes your fish 2-3 hours to finish their food, you are WAY overfeeding them. They should snatch up whatever you give them quickly and be done in a few minutes.

Turning off the waterfall shouldn't be necessary so they can eat - again, they should eagerly eat what you feed them very quickly. But more importantly, is your waterfall also your filtration? Because if it is, not only are you depriving the pond of a source of oxygenation for 4-6 hours a day, but you are probably killing off a lot of the good bacteria that is colonizing your filter media.

If your pond dimensions are correct, you aren't dealing with an overstocking issue, so that's good. What else can you tell us about your pond - is the waterfall your filter source? Do you have any other aeration in the pond? How old is your pond? Do you test your water quality?

 

[sissy]

Hi David and knew a lot of Demarest and went to school with several of them in Franklin Township .Could be chewing there food and also lack of oxygen and koi need a lot of it and do you know the temperature of the water that would help us

 

[Gordo33]

There are test kits for measuring dissolved oxygen . Your waterfall even if not used for filtration helps replenish oxygen into the water. I agree with Lisak1 feeding should only take several minutes and the WF should remain on . Other water parameters such as temp and pH can also affect oxygen levels

 

[David Demarest]

Thank you so much for the quick replies! Is there a certain time of day you want me to take the water’s temperature at? The pond is almost 15 years old. I’ll attach a picture of my father (who adored the pond) digging it. In the picture he’s standing tall and proud with his shovel, like he dug the thing by hand, but there happens to be a big orange backhoe in the background!

The waterfall has a bio filter media bag (looks like my mesh laundry bag from college with a bunch of black and red foam pieces in it), as well as a layer of hard green plastic filter material. I’ve seen it called “Matala”. Down at the opposite end is the filter box. In there, there is a net-like filter, another layer of “Matala” and on the other side, the pump. We wash out the net filter and the “Matala” (please tell me if there’s a better name for this stuff) three to five times a week to make sure the pump isn’t being overworked. We use a Tsurumi 50PN2.4S. I’ll attach pictures of the filter box, a shot of the pond, a picture of the food, how much I feed them (it’s a 12oz herring container that we fill about 3/4 of the way, sooo 9oz I guess), and a shot of the four koi. Let me know if you need pictures of anything else in order to help me. The three adult Koi are all about 14-16”, the “baby” is maybe 4.5”, the catfish is about 16-18”, and the sunny is maybe 6.5”. The sunny is very elusive. He lives in a cave, has dark coloring, and rarely comes out when people are there. In fact, we thought he had been snatched up by a bird for at least six months. One of my mom’s colleagues was a high school biology teacher and donated his fish to our pond at the end of his school year.


Yes, “Demarest” is a very popular New Jersey name. Apparently a lot of us that were “from the swamp” (translation of the name) felt NJ was a better place to live. We’re all the way up in northern NJ, but it’s good to know we’ve got relatives all over the state!

 

[mrsclem]

Hi David, if you are feeding that much food twice a day then you may be overdoing it. I have 7 large koi in one pond 18-34" and they get maybe a cup of food once a day and not every day. You have plants and algae for them to eat so they won't starve. I know it's easier to see the fish with the pump off but it should never be for more than a few minutes.

 

[Lisak1]

What a pretty pond! And your dad does indeed look proud!

So basically what you have is a biological filter on one end (that's the material in the waterfall box) and a mechanical filter in the other (the skimmer). You can rinse your filter material out, but it's best to do it in pond water so you don't kill any good bacteria with chlorine from the tap. I'm guessing you have to clean your skimmer as often as you do because of all the trees surrounding the pond - one drawback of a pretty setting I guess!

And yes - I would say you are feeding your fish far more than they need. We have double the number of koi you do and they don't get more than a couple handfuls twice a day. So cut way back on the food, keep the waterfall running, and watch them gobble up that food before you can blink an eye! There's plenty of other stuff for them to eat in the pond, so don't worry about them going hungry!

As for why are your fish clustering by the waterfall - could be oxygen, but they could also have learned that good stuff comes out of there when you turn it off and on. When I clean my bog or waterfall, mine line up like it's lunch time in the cafeteria.

Try changing the way you feed and see if the behavior continues.

 

[sissy]

I am lucky I get the time to feed my over 2 foot long koi 3 times a week

 

[sissy]

Well you had a lot of them .I went to school with the demarest twins and there were 8 children in that family and the grandfather owned a landscaping company that also mowed grass and plowed the snow .The grandfather had 4 boys and all of them had big families .I was born in PA raised in NJ and retired to VA

 

[David Demarest]

All great suggestions, and I will absolutely put them into practice. I recorded a video and a couple gifs of the pond running with the waterfall, so you can get an idea of the current. Unfortunately even the gifs are too big to upload, so they went to the Dropbox along with a walk around video of the pond with the waterfall on. I’m just concerned that a large portion—if not most—of the food will just get pushed into the skimmer box. I also am concerned for the little guy and even the sunny. They don’t scarf up the food like the others do. Is this just because I’ve been enforcing lazy eating by keeping the waterfall off for that long? Please take a look and let me know. Are fish like dogs in the sense that I’ll have to train this behavior out of them by reducing the amount of time the waterfall is on for? Or do you think if I just jump right into the habit of feeding them with the waterfall on that they’ll adapt quickly. They have been fed this way for the entire life in our pond, but I want to do what’s best for them and the pond. I just need to know how to go about it.

Here’s the Dropbox link again (please tell me if it’s not working):

https://www.dropbox.com/sh/kj8jbguxvfe6is5/AAAUN1RpZcTaknSYbsjCWoV_a?dl=0

 

[David Demarest]

Also, @Lisak1 do you mean I should turn off the waterfall, remove the black net filter and the green “Matala” from the skimmer box and just clean them off in the pond itself? The net might clean that way, but I think the “Matala” would be tough. I usually have to spray that stuff with the hose on full blast and the sprayer set to “jet” for 5 minutes on each side to clean out all the sludge. We wash everything into one of our gardens and it really helps the plants, so it’s not going to waste, but if you think the chlorine in the hose water (from the spigot on the outside of the house) isn’t good, then maybe this is another process I need to alter.

 

[Lisak1]

I would just start feeding them with the waterfall running - they'll catch on. Better yet - don't feed them for 2 or 3 days so they're really hungry. They'll be good and ready to eat then! And then just toss in a small handful. Stick around and watch them eat. If it goes in the skimmer, wait until the next day. If they aren't used to you standing and watching them eat, they may be skittish about coming to the surface at first. But hungry koi will eat. And it is more important that you keep that waterfall running - bacteria start to die off very quickly when you shut down the filter.

I don't actually have experience with cleaning filter media - we filter our pond with a constructed wetland filter. But I have read the advice to not use tap water on the bio-filter media. Most people will just pull it out and swish it in a bucket of pond water and then dump the bucket into the garden. I wouldn't worry about getting it squeaky clean - just enough so it isn't impeding the flow.

 

[Tara]

Hope everything works it's self out for you, your pond is lovely.

 

[Mmathis]

@David Demarest Matala is very easy to clean, but don’t clean it IN the pond — you don’t want the dirty water going back where it came from. The first thing you can do is hit the filter media against a bucket or something, and a lot of the crud will fall out. You can then either dip the filter in a bucket of clean pond water, or pour some clean pond water over it. If you can collect the dirty water, it’s great as fertilizer for your plants!

 

[mrsclem]

I have a 1000 gallon pump that I use to clean my filters. 12 feet of sump pump hose hooked to it, use the hose to spray off my filter media overtop of my flowers!