Fish dying in aquarium

[Ralph Parker]

Hello

I moved my fish from my 900-gallon pond outdoors into a new 125-gallon aquarium in my basement for the winter this September, since overwintering has not been successful in a 2' deep pond in Canadian winter. I moved in 2 ~9" butterfly koi, 2 comets/goldfish that has survived the previous winter ~7", 2 other comets that are ~5", and about a dozen babies that grew to maybe 2". I transplanted many plants from the pond, some red leafy plants that can be seen in my photos, and some water lettuce which has since died and been removed.

Yesterday almost all of the baby fish died over the course of the day, and the remaining 2 were found dead this morning. Additionally, starting the day before yesterday the water was slightly cloudy, but yesterday it was full out murky. Yesterday after finding the first few dead I did a ~40 gallon water change and added Seachem Prime and Aquascape beneficial Bacteria. I cleaned the filter media a few days ago, I am using 2 TopFin PF75 filters and I additionally have some bioballs behind the media in the filter.

I only thought to test my water after I did these things, I am getting <0.5ppm ammonia, 0.5ppm nitrites, 160ppm nitrates, pH of 7.6-7.8. Tested with API Master Test Kit.

As the babies were dying they often stayed very close to the top. The larger fish are now showing similar symptoms. I also noted red stripes on the tail of my white koi this morning which were not there previously, though that koi has been changing colours a bit for the last few weeks. There also seems to be a sort of film on the fishes' skin with bubbles and such attached to it. I don't know if this is atypical or if it's just because I've never stared at the fish this closely for this long before.

It is worth saying that the water is more of a green tinge of cloudy whereas it is browner in the photos, so I believe that the cloudiness may be an algae bloom...
There was leftover food yesterday morning which I removed and which is really atypical for these fish. I did not feed them yesterday evening.

I don't know how to proceed with this information. The biggest container I have is a 5-gallon bucket, and I feel like these fish are going to die really soon, but have no idea how to stop it.

Thank you in advance for the help.

 

[Ralph Parker]

I forgot to mention that, starting yesterday, I noticed quite a strong smell in the room where the tank is

 

[Mmathis]

I am so sorry to hear this -- what horrible news! But I don’t think there is much you can do for these fish, unless you can find a few more tanks that are very large (like several 50 gallon Rubbermaid-type totes) that you can spread them out with each fish in a larger container of water, with added filtration and aeration. What has happened is that by moving your fish into such tight quarters, your filtration has not been adequate to keep up with their waste products.

Please consider digging a deeper pond in this new year — deep enough that you don’t have to bring them in.

 

[Jhn]

Agree, with Mmathis the only shot you have is dividing them up in to separate tanks or tubs. The cloudiness in the tank is a bacterial bloom and the red streaking on the fins, hovering at the surface is a sign of ammonia poisoning. Water changes, adding prime or some other type of ammonia binding product May help until you get the fish separated. most Bacteria in a bottle is useless, one of the few I know of that is truly beneficial is fritz-zyme, that can help with the cycling process, which is what is happening in your tank along with it being overloaded with fish.

Hope your fish aren’t too far gone to save.

 

[JRS]

I would stop feeding for at least a week, do partial water changes of at least 30%, daily is not too much initially, until you get the water quality under control. If the plants are not doing good, they can add to the waste load on the tank. I would invest in a Python water changing system which makes large water changes much easier than the bucket brigade.

HOB filters typically do better in lightly stocked tanks due to the limited surface area of the media. Putting sponges on the intakes as prefilters can help and adds surface area for additional biological capacity. With heavy stocking like you have you need regular water changes at the very least to stay in balance. A large canister filter (or two) with substantial media chambers and high flow like an Eheim 2217 or Filstar XP3 would be a good investment if you plan on this setup long term.

I prefer bare bottom tanks for over wintering, especially with that many fish, it help the filters remove waste, any that is left can easily be siphoned off the bottom. I also like to keep something live in the tank off season to keep the biological filters active.

With that many large fish, over filtration, regular substantial water changes and light feeding are the key to good water quality.

 

[Lisak1]

With that many large fish, over filtration, regular substantial water changes and light feeding are the key to good water quality.

However at some point, it's simply too many fish for the tank. I think that's the situation here. I didn't keep track of the number but this sounds like too many fish for a 900 gallon pond to me.

Sorry for your troubles @Ralph Parker . Your fish should be able to survive in your pond. Maybe tell us a bit more about your set up and we can figure out what's happening outside.

 

[Mmathis]

@Lisak1, if I’m not mistaken, there wasn’t a problem when the fish were in the pond. The problems seem to have started after moving everything into a 125 gallon tank.

 

[poconojoe]

Seems to me that the tank is too small for the fish load.
Do you have an aerator running?

 

[Ralph Parker]

Hey, thanks for all the replies.

there wasn’t a problem when the fish were in the pond. The problems seem to have started after moving everything into a 125 gallon tank.

This is the case, there were never any problems in the pond (except when everything died in the winter). The problem started a couple of days ago, I moved the fish into the aquarium in late September

I would stop feeding for at least a week, do partial water changes of at least 30%, daily is not too much initially, until you get the water quality under control. If the plants are not doing good, they can add to the waste load on the tank.

Thanks for the advice, I will continue doing this.

Do you have an aerator running?

Yes, I am running this 250gph aerator using 2 airstones, on high.

Putting sponges on the intakes as prefilters can help and adds surface area for additional biological capacity. With heavy stocking like you have you need regular water changes at the very least to stay in balance. A large canister filter (or two) with substantial media chambers and high flow like an Eheim 2217 or Filstar XP3 would be a good investment if you plan on this setup long term.

I had been doing about 5 or 10 gallons once every week or two, I'll increase that now. Thanks for the suggestions, I'm definitely gonna add something around the prefilters. I'll look into better filtration too, thanks for the product suggestions, my current system does seem inadequate.

It is unfortunate that the aquarium seems to be too small, most of what I read suggested that my >2 gallons per inch of fish would be adequate. I knew it wouldn't be as nice as a full pond but didn't think it would be as fatal as the winters have proven to be.

So far none of the mature fish have died, and the water is looking a bit clearer. I'll keep changing the water etc and hope for the best

Thanks all!

 

[Ralph Parker]

I prefer bare bottom tanks for over wintering, especially with that many fish, it help the filters remove waste, any that is left can easily be siphoned off the bottom.

@JRS this interests me, I always thought that gravel substrate provided a good environment for bacteria to grow?

 

[JRS]

It does provide more surface area for beneficial bacteria growth but it becomes a liability if it is trapping waste that then decays in the tank. In the days when under gravel filters were standard, the flow of water through the gravel mitigated this since the gravel and its enormous surface area was the filter media; although you still had to regularly use a gravel cleaner to remove the silt.

As a decoration, without water flowing through it, there is much less oxygenated surface area for the good bacteria to grow. A tank with gravel may look clean until you stir it up and can cause issues in a heavily stocked tank like yours; especially if not cleaned regularly.

I have had overstocked winter holding tanks myself. Without gravel, my canister filter outputs sweep most of the crud off the bare bottom into the filter. Any decorations or weighted plastic plants can be moved and remaining accumulations of waste can be seen and easily siphoned out during water changes.

As you found out, the inch of fish rule can cause issues. A five inch goldfish, due to its mass, is much more of a load than 5 inches of tetras. Heavy filtration, aeration and tip top water quality through partial water changes is the key to keep it from going wrong.

 

[Lisak1]

(except when everything died in the winter).

there wasn’t a problem when the fish were in the pond

Well... that seems to be a tiny bit of a problem! That's why I posed the question. Maybe 2 feet deep isn't deep enough in your climate to overwinter fish, but total water volume for fish load can also be an issue. Or maybe it's how you manage the pond in the the winter. Keeping water circulating can be one solution. Some additional information would be helpful in that regard.

Bringing fish inside every winter will get harder as they grow larger and as was mentioned, reducing them from a 900 gallon pond to a tank indoors will always be a stressful situation. Six relatively small fish plus a bunch of babies doesn't seem like a lot, but two of those are koi. If they manage to survive, they will outgrow the pond for sure.

 

[Ralph Parker]

Hey, I figured that I'd post an update here. I ended up continuing daily ~20% water changes for a few days and adding prime daily. I also read that a bit of aquarium salt helps with nitrite so I added some of that. I also bought a UV filter and shortly after that the water cleared up super well. No more fish died so I still have the 4 comets and 2 koi in there now and they seem a lot healthier, they're not hanging out at the surface anymore. They actually were hanging out closer to the bottom for a while but I think they were just tired because they're acting pretty much normal now. The red disappeared from eh white one's tail. I started feeding them as well, gradually, less than before. I guess I got pretty lucky. I'll probably do about 5 gallons every few days for water changes from now on.

Or maybe it's how you manage the pond in the winter. Keeping water circulating can be one solution. Some additional information would be helpful in that regard.

I used this de-icing disk thing that keeps a hole in the water, I stop feeding when the water drops consistently below 20 degrees, I take out the annual/tropical plants. I take out the pump and filter since the tube to the waterfall goes underground and the waterfall I think would freeze. I had 2 airstones hooked up to an 8L/min aerator.

I've thought a few times about digging a deeper/bigger pond, but the issue with going deeper is that my town requires any body of water deeper than 2' to be fenced and locked off from the public, so I'd have to build a few different locked gates around. But I will probably have to do it eventually and I do want to for sure.

Thank you all for all your help!

 

[Mmathis]

The water definitely looks better, and the fish look better, as well. I was especially concerned about the black and white koi (sorry, don’t know proper koi color names) that appeared to have red streaking in its tail (which could have been an issue with the lighting), but he looks better.

I’m sure we’ve mentioned this already, but always keep in mind that good water quality is all about the balance of the chemicals and stuff in the water. With a smaller water volume, this balance is harder to maintain. Please be sure you are monitoring your water parameters!

 

[JRS]

Thanks for the update. Glad to see they are doing better.