A small koi switches between looking healthy, and floating

[Hop-frog]

I have a small koi that was living in a small 3-ft deep pond with about 40 other young fish. The other fish all seem to be doing fine, despite the weather getting cold, and occasional thin ice appearing at the top of the pond. Of these fish, I only lost one other koi this winter, about a month ago.

I noticed this particular fish bobbing in the current, drifting backwards by the current instead of swimming forwards. I scooped it out, and put it in a bucket (with pond water), to bring inside and slowly let it aclimize to room temperature, seeing if it would do better inside. When placed in an aquarium after 2 hours aclimitizing it spent 1-2 minutes swimming around frantically, possibly scared, then it stopped and started floating sideways at the top of the tank. I returned it to the bucket, where it returns to looking normal, and is no longer floating at the top.

Any ideas what is going on with the fish and what I can do about it?

 

[Lisak1]

40 fish in a too-small pond is my first guess. You said you only lost one other "this winter" but winter has only barely started. Are these all koi in this pond? All new fish to this pond? Did you breed these fish or did they come from a breeder in a batch? Lots of factors that can affect the outcome.

One thing to consider - 3 feet deep is good for overwintering koi, but you need water volume and surface area, too. If you put 40 fish in a 3 foot deep barrel of water, they'd all die. If you put 40 fish in a 3 foot deep cylinder - no matter how much water it holds - if the surface area is small they would probably also all die.

 

[Mmathis]

I have no idea what’s going on with the koi, but exactly where are you currently keeping your fish — IOW, what size pond or container? And how many koi are with these 40 other fish — IOW, how many koi do you have and how big are they?

Also, I don’t think you’ve ever told us (maybe you have and I missed it), but what filtration do you have?

I think that @Lisak1 might have hit on your problem.

 

[Hop-frog]

I bought the fish in the summer. They were living in two other ponds and a stream, but I am currently rebuilding the whole thing into one larger pond to finish in a couple of months, so I they are living in this temporary pool until it is finished.

It is approx. 2900 gallons, 3 feet deep, has two filters, pump rate of 4500 gph, with filters and media from the original pond, plant life, and all of the water came from the original pond too, I think more than sufficient size considering the small size of the fish.

There are about 40 goldfish, of various varieties, from koi, to comets, to ryukin, but all are about 1" to 2", only a few are more than 3". So no more than 80" of fish.

They all seem fine in the pond, but this one koi has been acting weird, swims fine one minute, the next it is sideways floating, backwards with the current, then returns to looking healthy like the others.

The weather has been swinging like a pendulum from 29 degrees F to 60 degrees F, so the ice comes and goes. I don't know if the fish are having trouble hibernating, as they seem to hibernate for a few days, then the weather returns to comfortable temperatures and they are back to swimming around.

 

[Lisak1]

I have a small koi that was living in a small 3-ft deep pond with about 40 other young fish.

Ok - you and I define "small" differently. Nearly 3000 gallons should be fine for what sounds like a bunch of goldfish.

Fish don't have "trouble hibernating". (They don't technically hibernate at all, but that's for another conversation.) Even though your air temps are fluctuating, water temperature changes very slowly so that would have little effect on your fish. Your fish may be reacting badly to the move - even with our best efforts, those things can be stressful for fish. I'd stop moving it in and out if I were you as that will only exacerbate the stress.

I guess I'm just basically confused about the whole story - how many ponds, streams, temporary ponds, and future ponds are we talking about? Are these all your ponds? Why did they have to move from the old ponds before the new pond was ready? What kind of temporary pool holds 3000 gallons of water?

 

[Hop-frog]

I moved into a new house last summer. The backyard being completely bare dirt, I decided to turn it into a series of ponds. The design had three small pools, plus a river area, totally 20,000 gallons, connected in a sequence. I finished everything but the river portion, and setup the pumps and added fish, some which I had moved from indoor aquariums.

Though my house is not listed as being in a flooding zone, a flash flood came, and I realized the installation was insufficient. The flood waters came down instantly, flooding to knee-height, filling the unfinished river area with mud, and causing one portion of the pond to sink substantially. I realized that the pond design was too precarious, and had the potential to bring disaster should another flash flood come, so I returned to the drawing board. Particularly fragile was having multiple pools that flowed to the next...leaving many potential places for failure.

Now I had the fish all moved to a temporary 3,000 gallon INTEX pool and I'm building a single 37,000 gallon pond, with a much stronger, simpler design, using a concrete foundation, plus metal reinforcement. It will take several more months yet to complete, but will leave me with a design I don't have to worry about if I am away on holiday, and progress already reveals it looks much nicer than the original over-complicated design.

 

[Lisak1]

Again - you say "three small pools" and then "20,000 gallons". There's nothing small about that!

 

[Mmathis]

Also, we keep hearing 20,000 gallons, 30,000 gallons, and now 37,000. Just curious, but how are you calculating these volumes? With a huge pond, it might not be an issue, but with smaller ponds, it’s important to be as close as possible to your “number of gallons.” This is important when figuring filtration, fish load, or if you ever have to treat the pond for anything like parasites or a bacterial infestation.

I’m sorry you had an issue with high water and run-off! That’s something that many pond owners don’t take into consideration when choosing a location and building the pond. At least you are looking at it from the start so you can make appropriate plans. We have a very high water table here (or, at least we did in our other house — current house is in a different neighborhood) — this is Louisiana. Fortunately we never had any yard flooding, but I did build the sides of the pond up to keep yard water from entering. Our current house (moved 2 years ago) has a higher elevation and we’re within view of a small lake that’s part of the neighborhood. We’re not in a flood zone here, either, due to our elevation (we looked at flood maps for the past gazillion or so years before we signed the papers), but you just never know what Mother Nature is going to throw at you!

 

[Hop-frog]

The size grew after I found a guy to dig out the middle, and decided to go 6 ft deep instead of 4 ft deep.

At least I gained experience from building the first pond. I'm much happier with the new design too.

 

[JamieB]

I’ve so been there!!!! Started digging a pond, had flood show me the error of my plans, and ended up moving the location and going bigger! Which reminds me, I really should fill that first hole back in come spring....
So, this one koi. I believe it may be stressed and possibly ill. Set it in the aquarium, give it time, and plenty of places and plants to hide in. I would have just enough water flow to filter the water, to reduce the stress of swimming against the current. If the aquarium is in a busy part of the home, use some basic craft paint and paint the glass( presuming it’s a glass aquarium, leaving you several areas to peek and check with out lifting the lid. Craft paint can be scraped off or washed off if you just do the water based acrylic in the craft section of Walmart. I’ve used it on back and sides of aquariums, then scraped it off later, only to paint it a different color design later. Pick a simple dark color, that will let the fish feel hidden and let it rest. If it starts presenting other symptoms, then we can help figure out the problem.