r/Koi

Hello everyone,

A few weeks ago I bought a house that came with a pond and koi. The previous owner told me there were 4 koi, and that the pond had been completely self-sufficient for 40 years (no filter, no pump, and she didn't feed them apart from a few oat flakes now and then as a treat). So I wasn't too concerned and just did some light maintenance : removing fallen leaves and spent lily pads, and topping up the water level as it evaporated. I bought them koi sticks and gave them a few every 3-4 days. I've only ever seen 3 koi; I don't know what happened to the fourth. They are about 30cm long.

The trouble started a few days ago. Around midday I found one koi in severe distress, floating on its side. I did some quick research and understood it was likely oxygen deprivation. I rushed out to buy an air pump and installed it as fast as I could (2 × 180 L/h). She disappeared for a few hours and then, miraculously, reappeared that evening as if nothing had happened, though perhaps slightly less lively. I also took the opportunity to test the water and everything looked fine: temperature 22°C, pH 8, KH 300 ppm, ammonia, nitrite and nitrate all undetectable.

She seemed fine for two days, then I found her again at midday in severe distress. No miracle this time, I didn't see her at all for two days and eventually found her sunk at the bottom, half-buried in the sludge. I think she had been dead for a while, but the water is so murky that I hadn't spotted her despite searching.

A second koi looks swollen towards the rear of her body and I'm very worried the same thing will happen again. I've read this can be very serious (dropsy) or completely benign (overweight, constipation, eggs), and I'd really appreciate your opinion based on these photos. I have no baseline to know whether she's been like this for a long time or whether it's recent, and whether it's progressing.

These koi lived 40 years without any problem, and as soon as I take over responsibility for them, one dies and another may have a serious condition.

Since then I've researched as much as I could and I'd like to give them better living conditions.

I've realised there were signs throughout the summer heat that they were all short of oxygen and I failed to interpret them : they were often coming up to gulp at the surface. Since installing the air pump, the two survivors seem far more comfortable.

I've also ordered a filter (Oase BioPress Set 4000, 1500 L/h) and a pond vacuum to remove the sludge at the bottom, both due to arrive in a few days (there's a very thick layer and I've read this can be dangerous for them?). I gather I should wait for cooler weather before using the vacuum, but on the other hand I don't want to leave it too long: at what water temperature can I safely do it?

Regarding the pond volume, I get the impression it's far too small but I don't really see what else I can do. I've estimated around 1,700 litres, with a maximum depth of 40 cm (perhaps more once I've removed the sludge?), and dimensions of 1,70 × 2,50 m. It's shaded by a big tree throughout most of the day.

Is there anything else I should be putting in place to help them?

I also have a lot of questions about feeding, I don't know how much to give them. I don't know what's too much or too little. I've read you should give what they can eat in a few minutes, but it seems that as long as I keep giving, they keep eating.

I know this message is very long, I have a lot of questions and I really want to get this right. I really thank you for any advice you can offer.

For reference: photos of the swollen koi, of the healthy one, and of the pond.

Just posting some pictures of my koi haha. Would love to hear what ya think!

I just noticed my white koi has these weird bumps on his side between his fins and tail.

Does anyone know what this may be? All the water levels are normal.

PS. Yes I'm aware his tail is upturned, no I will not cull him.

Had a mass removed on my leg a little over a week ago. Of course these kids choose to spawn for days when I'm hobbling about 🤦

Wondering exactly what this koi is? Also if it is of good quality. It’s about 7 inches right now, nice thick body.

Two of my Koi have pink, raised, fleshy bumps on their sides. No changes in behavior or appetite. Water parameters are great. It is August in Southern California, so the water is the warmest it has been. Can carp pox develop even with the water temperature at 80°?

This was our favorite koi that we’ve had over 10 years. He was so friendly, came up to everyone and one of the best and most fun fish to watch in the pond. I’m really sad because it was a preventable death and we are fully responsible for their care and I feel like we failed him. I’m just really sad today and no one understands because “it’s just a fish.” We buried him in the backyard earlier. This hobby sucks sometimes! We’ve lost a couple fish to random reasons over the years and it never gets easier especially when it’s one of your faves. None of my other fish come to eat out of our hands, so that part sucks. Anyway just wanting to vent to the void thanks for reading and watching. He was so much bigger than we realized over 2.5 foot. We called him Tano.

I feel like I’ve watched 500 videos on TikTok and some on YouTube of how to do this but for some reason, I’m still confused. I think I’m getting two different kind of fog filters confused like some of them have this PVC pipe going from the bottom of the fog filter all the way up to the top and sticking straight out and then others don’t have that at all I’m just confused. Basically I want to turn this tote into a bog filter that has peagravel on the top that I could put plants in I have four 1” bulkhead fittings and four 1.5” I also have a drill of Course but not sure what size hole saw to use for my 1” and 1.5” bulkhead fittings, and I have a tote and that is all. Would anybody possibly be able to tell me what exactly I need to do this? Or why I’m getting so confused am I getting two different filter styles mixed up or am I just dumb?

Hi guys,

I need some help identifying what’s going on with my koi fish so I can treat it. I’ve already tried calling local fish doctors/petsmart but need a second opinion.

About 1.5 months ago, I noticed sudden bloating in my koi fish. I thought it was a case of constipation and started feeding deshelled peas and fasting every other day or two days.

I didn’t notice a huge difference and eventually returned to regular food (the Hakari goldfish excel purple bag). The koi has always had a huge appetite and eats very fast.

For context, my tank is 85 gallons and has 1 koi (~7in), one common goldfish (~4in), and 1 pleco. I do consider this overstocked and I have plans to build an outdoor pond and transfer them outside in the future.

They do have a balanced diet of the pellets, and Repashy super gold but mainly the former.

Like a month ago I noticed the right side of the koi’s stomach start to bulge abnormally in a concentrated spot (see the pictures), and I started to think this wasn’t constipation and maybe an illness. It’s been growing bit by bit ever since. I still don’t have a clear answer.

I called one doctor and they explained that if the pellets have wheat flour, this can stick to the koi’s inner lining during the summer and it can’t digest it — causing dropsy.

A week ago, I moved the koi to a 20g quarantine tank and started doing epsom salt dips, keeping the tank at 0.3ppm, and dosing kanaplex (regular treatment dosage). This hasn’t helped!

Before this, the koi has not showed any signs of lethargy, was eating regularly and showing no pineconing symptoms. I think the koi has been unhappy and lethargic without adequate space to swim. After moving to the quarantine tank, I have fasted for a week, and only just decided today to move it back to the main tank today because I feel like I’ve concluded it is not dropsy (which should be symmetrical swelling??). I’ve fed peas again tonight.

PH level is 8.0, ammonia is 0, nitrate is 0, nitrite is a little high at 0.25. I can do a water change tmr but don’t want to stress the fish out more tonight.

Google says this bulge can be a tumor or egg-bound issues. I don’t know the gender of the fish but the goldfish tends to butt its head into the koi during feeding, never the other way around. Also, recently the koi has started to lean a little to the right when swimming :(

Please, can someone help diagnose this issue? It’s really frustrating not knowing the real issue and getting all different kinds of answers. I’m really concerned that with time, the koi will show worst symptoms and I’m really scared.

I also plan to call an actual fish vet on Monday that might be able to see the fish in-person (don’t know for sure).

(First picture is a month ago, 2nd picture is today).

Any replies will help! Thank you and apologies in advance for the long post.

We have about 13 koi. Most are around 20 inches, our biggest being almost 26 inches and she is only four!

3000gallons, had nine of my big old fish die this year and I started again with some new 4” koi from local dealer. Bottom drain, sieve, econobead and uv.
I have one bigger original left.
I have always wanted to hand feed and done it for first time yesterday, loved it 😀
Got a video today feeding them cooked prawns
Hope you like

From Hoshikin koi farm. Jumbo tosai both about 12-14”