Active and ravenous but thin with long stringy poop

I have had four Melanotaenia australis, Western rainbowfish, for about six months now but one of them stands out for the wrong reasons.

It is the longest of the four but by far thinner and hungrier than the others and almost constantly drags around a long string of poop. Its behaviour is not otherwise unusual - it is active and will indulge in the occasional chase of one of the others. There are no clamped fins or subdued behaviour, quite the opposite.

I suspected that there might be a gut parasite problem and have dosed the tank with Flubendazole (NT Labs Anti-Fluke & Wormer). I'm in the middle of the second week and second dosing.

I've also upped feeding and I think this is helping as it no longer looks quite as thin as it once did. I guess it's a female as it does not exhibit the taller body of the one example I have that is definitely male.

However, the stringy poop problem remains. It appears that food consumed travels through the gut very fast. The string is quite thick soon after feeding. It becomes thinner and loses the colour of the food recently consumed later. It does now occasionally break off, which is one small improvement compared to two weeks ago.

That's as much information I think I can provide - can anyone add any helpful comments? Thanks in advance.

PS Tankmates are Platys and Pepper Corys. It's a long-established moderately planted tank but not with fast growing plants. 120L tank with an over-sized (rated for 200 litre tanks) external canister filter. No no nitrites or ammonia, water is quite hard.

Fish do a stringy white poop for several reasons.
1) Internal Bacterial Infections causes the fish to stop eating, swell up like a balloon, breath heavily at surface or near a filter outlet, do stringy white poop, and die within 24-48 hours of showing these symptoms. This cannot normally be cured because massive internal organ failure has already occurred.


2) Internal Protozoan Infections cause the fish to lose weight rapidly (over a week or two), fish continues to eat and swim around but not as much as normal, does stringy white poop. If not treated the fish dies a week or so after these symptoms appear. Metronidazole normally works well for this.

There is a medication (API General Cure) that contains Praziquantel and Metronidazole and might be worth trying.

It's interesting that API and the Californian government have listed Metronidazole as a carcinogen. That's a concern considering it was widely used to treat intestinal infections in people.

Anyway, handle with care, don't inhale the medication, and wash hands with soapy water after treating the fish or working in the tank.


3) Intestinal Worms like tapeworm and threadworms cause the fish to lose weight, continue eating and swimming normally, do a stringy white poop. Fish can do this for months and not be too badly affected. In some cases, fish with bad worm infestation will actually gain weight and get fat and look like a pregnant guppy. This is due to the huge number of worms inside the fish.

If the fish is eating well and been swimming around normally then it's most likely intestinal worms.

You can use Praziquantel to treat tapeworm and gill flukes. And Levamisole to treat thread/ round worms. If you can't find these medications, look for Flubendazole.

Remove carbon from filters before treatment and increase aeration/ surface turbulence to maximise oxygen levels in the water.

You treat the fish once a week for 4 weeks. The first treatment will kill any worms in the fish. The second, third and forth treatments kill any baby worms that hatch from eggs inside the fish's digestive tract.

You do a 75% water change and complete gravel clean 24-48 hours after treatment. Clean the filter 24 hours after treatment too.

Treat every fish tank in the house at the same time.

Do not use the 2 medications together. If you want to treat both medications in a short space of time, use Praziquantel on day one. Do a 75% water change and gravel clean the substrate on day 2 & 3. Treat the tank with Levamisole on day 4 and do a 75% water change and gravel clean on day 5, 6 & 7 and then start with Praziquantel again on day 8.

The water changes will remove most of the medication so you don't overdose the fish. The gravel cleaning will suck out any worms and eggs that have been expelled by the fish. Repeating the treatment for 3-4 doses at weekly intervals will kill any worms that hatch from eggs. At the end of the treatment you will have healthier fish.

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If you can post a picture of the fish it will help with identifying the problem and I can tell you what sex it is.

If the pictures are too big for the website, set the camera's resolution to its lowest setting and take some more. The lower resolution will make the images smaller and they should fit on this website. Check the pictures on your pc and find a couple that are clear and show the problem, and post them here. Make sure you turn the camera's resolution back up after you have taken the pics otherwise all your pictures will be small.

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What are you feeding the rainbows?

I had one doing the same thing. I was told he had gill flukes and I possible intestinal parasites. I tried the General Cure and later tried Prazi Pro. Tried everything but sadly he passed away this morning. I wish you better luck.

@Colin_T Many thanks for that. As I mentioned, I'm into the second week and dose of Flubenzadole. I did a 60% water change inbetween doses but didn't clean the filter - it had been cleaned 3 weeks before. I will clean it this weekend when I prepare for the third dose of Flubenzadole.

The NT Labs Anti-Fluke & Wormer (Flubenzadole) instructions say three doses - do you think a fourth will be beneficial?

Regarding the filter clean; my usual routine is to not touch the ceramic filter media at all, only gently flushing with tank water I'm about to dispose of, but I do rinse out the sponges thoroughly and sometimes in tap water.

I might try to cover the protozoan infection possibility after finishing with the Flubenzadole, so that won't be for a week or two. A couple of my Platys behave oddly and I wonder if a protozoan infection might explain this but I'll start a different thread.

They get fed standard flakes most of the time, and once a week they get some (rehydrated) dried tubifex worms that come concentrated into dried-out cubes. The Corys get sinking pellets and I've seen the other fish pecking at these on the gravel.

I've just realised you are in Western Australia - where my Rainbowfish live in the wild (I guess)? I'm a Brit but was born on the other side of your country in Newcastle - not been back for 56 years though..

I'll get some photos done when the tank lights are on this evening

Deanasue said:

I had one doing the same thing. I was told he had gill flukes and I possible intestinal parasites. I tried the General Cure and later tried Prazi Pro. Tried everything but sadly he passed away this morning. I wish you better luck.

Click to expand...

Sorry to hear that - were the symptoms the same? By that I mean always hungry but thin but remaining active? What kind of fish? Thanks.

All filter media/ material should be cleaned in a bucket of tank water, rather than under tap water.

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You can do 3 or 4 doses at weekly intervals. If the water is warm then 3 doses should be fine. If the water is cool then 4 doses is better because the worm eggs take a bit longer to hatch in cooler water.

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If the problem has been going on for 6 months it won't be an internal protozoan or bacterial infection. Internal bacterial infections kill fish within a few days. Internal protozoan infections kill fish within 2 weeks of showing stringy white poop.

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Rainbowfish need plant matter in their diet. You can use goldfish flakes, vege flakes, live aquarium plants like Duckweed, or stuff like marine algae, spinach, cucumber, pumpkin, zucchini. The aquarium plants and marine algae are better for them and easier for them to digest.

You can grow duckweed in plastic storage containers outdoors and bring some in for the fish to eat.

They also eat prawn/ shrimp, aquatic crustaceans, small insects like moths, flies, ants, ant eggs, aphids and most other small non poisonous insects.

I used marine green as part of their diet. This is a frozen food from pet shops and contains prawn, fish, squid and algae.

iburley said:

Sorry to hear that - were the symptoms the same? By that I mean always hungry but thin but remaining active? What kind of fish? Thanks.

Click to expand...

Mine was a leopard danio. He started just st getting thinner than the others and eventually couldn’t eat and wasted away. I even tried Spectogram which is a mixture of Kanamycin antibiotic and Furan-2 and nothing helped. Please keep us posted on how yours does.

Here is the dodgy fish before feeding.



This is the big male in the group with the unwell fish in the background.



Here is hungry fish about an hour after feeding.

Deanasue said:

Mine was a leopard danio. He started just st getting thinner than the others and eventually couldn’t eat and wasted away. I even tried Spectogram which is a mixture of Kanamycin antibiotic and Furan-2 and nothing helped. Please keep us posted on how yours does.

Click to expand...

My one does look to have put on a little weight but is still noticeably thinner than the others, especially if viewed head-on. But it's the poop situation that looks worrying the most as you can see in my photos.

Colin_T said:

All filter media/ material should be cleaned in a bucket of tank water, rather than under tap water.

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You can do 3 or 4 doses at weekly intervals. If the water is warm then 3 doses should be fine. If the water is cool then 4 doses is better because the worm eggs take a bit longer to hatch in cooler water.

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If the problem has been going on for 6 months it won't be an internal protozoan or bacterial infection. Internal bacterial infections kill fish within a few days. Internal protozoan infections kill fish within 2 weeks of showing stringy white poop.

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Rainbowfish need plant matter in their diet. You can use goldfish flakes, vege flakes, live aquarium plants like Duckweed, or stuff like marine algae, spinach, cucumber, pumpkin, zucchini. The aquarium plants and marine algae are better for them and easier for them to digest.

You can grow duckweed in plastic storage containers outdoors and bring some in for the fish to eat.

They also eat prawn/ shrimp, aquatic crustaceans, small insects like moths, flies, ants, ant eggs, aphids and most other small non poisonous insects.

I used marine green as part of their diet. This is a frozen food from pet shops and contains prawn, fish, squid and algae.

Click to expand...

Come to think of it I did actually rinse out the sponges in tank water last time though I do sometimes rinse in tap water if they are very badly clogged. My thinking is that the ceramic media is not disturbed and that's where most of the important biological processing goes on.

The water is 23C so this is a warm-ish tank, definitely not cold water.

The problem with the Rainbowfish is definitely months and not weeks.

Thanks for the advice on feed - I will add more fresh plant matter ASAP.

Beneficial filter bacteria live on any hard surface including ceramic beads, noodles, sponge, filter floss, etc. They also live on the substrate but huge numbers live on filter media because there is lots of area for them to grow and a constant flow of oxygen rich water that has food in it.

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I would dose the tank 4 times with the dewormer just to make sure.

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Does the poop ever come off the fish completely, or is there always a bit attached to the body?

I have concerns the bit hanging off the fish is actually the intestine that might have separated from the fish's butt and is now just hanging out of the body.

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Feed the fish 3-5 times per day for the next month and do lots of big water changes and gravel cleans to keep the tank clean.

Colin_T said:

Beneficial filter bacteria live on any hard surface including ceramic beads, noodles, sponge, filter floss, etc. They also live on the substrate but huge numbers live on filter media because there is lots of area for them to grow and a constant flow of oxygen rich water that has food in it.

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I would dose the tank 4 times with the dewormer just to make sure.

--------------------------
Does the poop ever come off the fish completely, or is there always a bit attached to the body?

I have concerns the bit hanging off the fish is actually the intestine that might have separated from the fish's butt and is now just hanging out of the body.

--------------------------
Feed the fish 3-5 times per day for the next month and do lots of big water changes and gravel cleans to keep the tank clean.

Click to expand...

OK, I will go with a fourth dose.

Yes the poop does detach completely at times. As I said, the fish in question seems to behave normally apart from the ravenous appetite and poop problem.

I have been giving them double or even triple portions in the last ten days as it does tend to get get consumed quickly!

I'm keeping on top of uneaten food with gravel cleaning an a large water changed at the weekend. I'm also testing regularly and there are no ammonia or nitrite showing. I'll do a bit of pruning in the tank as well this weekend.

It's feeding time again and I've just dropped some very finely chopped courgette (zucchini) into the tank. I think most of what was snapped up promptly came back out again - but let's see!

Update: I will be administering the fourth weekly dose of Flubendazole this weekend. Frustratingly, I can't really say the long poop problem has changed. However, the fish has put on a little weight and no longer looks emaciated. But it still looks thinner than the others. It's still as active and hungry as usual.

I've switched from generic fish flakes to green spirulina-based ones (JBL) for now.

One surprise was spotting a couple of tiny snails near the top of the tank, which I removed. These must have been on some plants I added earlier in the week. I thought Flubendazole kills snails - so that was odd.

Keep feeding the fish 3-5 times a day for the next month because it takes a good month for them to recover after having intestinal worms.

As long as the poop isn't white or clear it's not that much of an issue.

When the fish get more plant matter it should come off easier and be less likely to hang around.