Fish-eating Mystery

Hello Aquarist Community,

I have an interesting situation that occurred in my planted 24-gallon tank. I had recently purchased 6 new cardinal tetras to add to my previous collection of 6 serpaes and 2 cardinals. In retrospect, I should have quarantined the newbies but being a novice, I put them straight into the tank. HUGE MISTAKE. The next day one of the new cardinals died and within a week I had lost 4 cardinals - no serpaes. What I initially thought was that the serpaes were fin-nipping at the tails of the cardinals (which could have caused secondary infection like tail rot). BUT, very rapidly I noticed several had their coloration fade, they started to swim solo and display weird/lethargic based swimming behaviour and then DIE within days of each other.

When my long-time and fully-grown cardinal got infected and died, I knew it was some nasty disease spreading fast. Melafix and Primafix did not work...isolated the other cardinals using Paraguard for 4 days which seemed to prevent further deaths but tails are almost to the base. I have started to notice that my serpaes are now developing fraying of the tails, and have white granules on their bodies (thought it may be Ich), but doesn't appear to get worse with time.

But here is where the story gets interesting... So 3 cardinals had died at this point (RIP) and I had put them in a container meaning to return the fish to Petsmart for a refund... but when I checked a week later the container was filled with worms and absolutely no remnants of the three fish I put in there. The worms are small about 0.5cm and clear, except for the brown intestines inside (presumably my eaten fish).

So fish community...
1) What is this outbreak I am dealing with and has anyone dealt with something similar? Could it be columnaris?

2) What are those worms and how did they get there? (The container does have small pen-tip sized holes in it (from previous usage) so could it be some insect larvae?

Thank you!

 

Could you post pictures?

Based on your description, it sounds like the fish definitely came with something. Probably either internal parasites (worms) or bacteria...

Progression pictures would be awesome here, but any pic would be better than nothing. When you say their color faded, did it go in patches or pretty evenly? When they lost their tails, did it erode from one edge, or did the whole thing turn clear and then kinda rot away at the same time?

The worms sound like detritus worms (you get them whenever there is high ammonia, which decomposing bodies will definitely produce) but it could also be what killed the fish if the worms were there before the fish died... could you take a picture?

I'm really sorry you have to deal with this and I hope your remaining fish make full recoveries

 

So today another of the cardinals died. I thought the paraguard had fixed the problems so I moved the quarantined cardinals back into the planted 24g, but another one died today. I have attached a picture of the tail-rot on the dead cardinal, as well as the behaviour it showed before it died.

As for the serpaes, I could not get any clear photos, only a video which I can't seem to upload here. I have a picture of the worms:

 

I am currently attempting fish in cycling (which I know is not the preferred method) and have this tank with built in filter () which is 29l and I have two female Bettas I was wondering if this style of filter would be able to cycle because it is a drop down style. I have been doing water changes 2-3 times a day ‍♂️ I didn’t know if this was down to the style filter

I know this isn’t the best place to post but I saw it got fast replies and need advice

 

Worms:

 

I think that just as you suspected, you introduced Cardinal Tetras with columnaris that spread to the others.

The worm appears to be a flatworm.

 

That worm is a heliminth(flat worm,fluke).

There are three major groups of parasitic worms:

Nematodes(roundworms)

Helminths(flat worm)

Trematodes(tapeworms)

Unfortunately, Helminths are known to use fish as an intermediate host in order to get into organisms that feed on them. Out of the ~30,000 helminths that parasitise fish, some are even known to use humans as a primary host.

I recommend consulting a veterinarian. It may be expensive, but it may save you the trouble of tearing down the tank in order to remove a potentially dangerous parasite from your aquarium.

I would also be wary of any fish purchased from that particular retailer. I find when things as bad as this are introduced into your aquarium, the seller violated any customer-seller trust; and needs to take responsibility for an absolute fiasco like this. If they refuse, they are not worth your time; so take your business somewhere else.

 

That worm is a heliminth(flat worm,fluke).

There are three major groups of parasitic worms:

Nematodes(roundworms)

Helminths(flat worm)

Trematodes(tapeworms)

Unfortunately, Helminths are known to use fish as an intermediate host in order to get into organisms that feed on them. Out of the ~30,000 helminths that parasitise fish, some are even known to use humans as a primary host.

I recommend consulting a veterinarian. It may be expensive, but it may save you the trouble of tearing down the tank in order to remove a potentially dangerous parasite from your aquarium.

I would also be wary of any fish purchased from that particular retailer. I find when things as bad as this are introduced into your aquarium, the seller violated any customer-seller trust; and needs to take responsibility for an absolute fiasco like this. If they refuse, they are not worth your time; so take your business somewhere else.

Yeah, I usually buy my fish from Big Al's and have never had a problem, but thought a few cardinals would be fine from Petsmart. Won't be giving them my business again for fish. As for treating this, does anyone have any suggestions? Should I just go and buy Kanaplex to deal with possible columnaris? I feel I could lose my whole stock this week.

 

I am currently attempting fish in cycling (which I know is not the preferred method) and have this tank with built in filter () which is 29l and I have two female Bettas I was wondering if this style of filter would be able to cycle because it is a drop down style. I have been doing water changes 2-3 times a day ‍♂️ I didn’t know if this was down to the style filter

I know this isn’t the best place to post but I saw it got fast replies and need advice

You need to post under "freshwater beginners" so you can get the help you need. It's not nice to hijack someone else's post, you will most likely get ignored, and you won't be notified about any replies. If you find that you're not getting answers on the main fourm, you can change the title of your post (you've kinda got to play click-bait here). There are a lot of other posts about cycling, so you can also search the fourm for "cycle" or "cycling" and it'll bring a bunch of posts up and that might get you the info you need.

Furthermore, 29l (7.5g) is waayyy to small for two female bettas and there needs to be more than 2 bettas, UNLESS they're separated. And even then... Also, 2-3 water changes a day is too much. Do you have a water test kit? If so, you need to be checking your perameters 1-2 times a day and only doing water changes when the ammonia gets too high (I believe it's .50ppm or higher?). Changing the water too much can stress your fish out. The link just takes me to Google, so idk what filter/tank you have but as long as your filter pumps water and has some form of filter media (a sponge, bio balls, etc.) It should be fine. The main thing is you want a place for your benifital bacteria to grow and water flow.

If you have more questions, you can pm me or make another post on the main forum.. good luck