55 Gallon Tank Mysterious Disease Slowly Killing Fish 1 by 1

To get this out of the way, I have a 55 gallon tank with moderate stocking, 1 angelfish (her mate died a long time ago), 1 apisto mcmasteri, 2 honey gouramis, 1 sunset thick lip gourami, 12 x ray tetras, 12 cories, and 1 BN pleco. The nitrogenous wastes are 0 except for nitrate which varies from 5-10, my plant load and tons of water sprite keep that very low. So this issue is not a nitrogen cycle thing.
Over the past year and a half, very slowly, something has been killing my fish. First it was my peacock gudgeons so I've just given up trying to keep them. My gouramis typically die to dropsy, they just stop eating and blow up after a while. The fish usually die about 6 months after I originally introduce them to the tank after a 4 week quarantine. At first it was just gouramis and the gudgeons but over the past few months my tetras have started dying and my apisto hongsloi got really pale and croaked within a few days. The time this disease takes to kill varies from days to weeks, and just over the weekend I lost another tetra and my thick lip gourami is showing dropsy, but they were fine a few days ago.
This issue seems to be very persistent, and I'm getting really close to just giving up, I do my water changes and keep up with the work like I should but the fish just keep dying horrible deaths. Is there some bacteria just living the tank killing my fish? Is there anything I can do short of putting down all my fish and plants and blasting the tank and everything in it with methylene blue or something else to kill any bacteria?

 

Aww that's so sad I can't help a ton with knowing what disease is hurting your tank, but I wouldn't give up yet! Have you tried any general tank medication and how new are these fish?

 

Aww that's so sad I can't help a ton with knowing what disease is hurting your tank, but I wouldn't give up yet! Have you tried any general tank medication and how new are these fish?

No fish added in the past few months, I medicated the tank with some metronidazole flakes a while back but the fish didn't like it because it's notorious for tasting bad. Other than that I've tried to treat the affected fish with meth blue + salt baths but that has not worked.

 

Ok. The gouramis seem to be dying from dwarf gourami disease. It's possible that multiple diseases could be affecting your tank. What signs of disease if any are the fish showing? A copper based medicine might work for the tank but might injure or kill your water sprite. Is it possible that the fish are dying from old age?

 

It would help to fill out the emergency template so we have all your tank details. Will at least take care of checking off the standard things... do you have a heater, do you use a dechlorinator, is the food appropriate, ph in range, etc.

 

I agree with sunflower. This will help to know exactly what's wrong with the tank

 

Tank
What is the water volume of the tank?
55 US gal
How long has the tank been running?
~3 years
Does it have a filter?
2 HOB filters rated for 50 gallon tanks
Does it have a heater?
2 heaters, one for backup
What is the water temperature?
78
What is the entire stocking of this tank? (Please list all fish and inverts.)
3x nerite snail
1x angelfish
1x apist mcmasteri
12x x ray tetra
12x cory
1x bn pleco
2x honey gourami
1x sunset thick lip gourami

Maintenance
How often do you change the water?
once per week
How much of the water do you change?
30%
What do you use to treat your water?
prime
Do you vacuum the substrate or just the water?
substrate vac

*Parameters - Very Important
Did you cycle your tank before adding fish?
yes the tank is several years mature
What do you use to test the water?
master freshwater test kit
What are your parameters? We need to know the exact numbers, not just “fine” or “safe”.
Ammonia: 0
Nitrite: 0
Nitrate: 5-10
pH: 6.8

Feeding
How often do you feed your fish?
once per day
How much do you feed your fish?
not sure how to answer this, weight? time to eat? typically all they eat in a few mins
What brand of food do you feed your fish?
Angels plus, omega one, hikari
Do you feed frozen?
yes
Do you feed freeze-dried foods?
yes

Illness & Symptoms
How long have you had this fish?
- typically 6 months before they die
How long ago did you first notice these symptoms?
- 1.5 years ago
In a few words, can you explain the symptoms?
- fish stops eating, occaisionally gets dropsy
Have you started any treatment for the illness?
- meth blue baths with salt
Was your fish physically ill or injured upon purchase?
- no
How has its behavior and appearance changed, if at all?
- sluggish, pale

Explain your emergency situation in detail.
(Please give a clear explanation of what is going on, include details from the beginning of the illness leading up to now)
see OP

It would help to fill out the emergency template so we have all your tank details. Will at least take care of checking off the standard things... do you have a heater, do you use a dechlorinator, is the food appropriate, ph in range, etc.

 

This happened to me with my Kribs. One day they just started bloating and gasping at the surface (slow progression) and dying. One by one. I had a thread on it Y’all are my only resource....Kanaplex for dropsy?! | Freshwater Fish Disease and Fish Health Forum | 477899
I treated with kanaplex as told after I think two fish died (maybe three I have to reread the thread) and then another was still sick so I did another round of kanaplex. Hope this helps!

 

Ok. The gouramis seem to be dying from dwarf gourami disease. It's possible that multiple diseases could be affecting your tank. What signs of disease if any are the fish showing? A copper based medicine might work for the tank but might injure or kill your water sprite. Is it possible that the fish are dying from old age?

it wouldn't be dwarf gourami disease since the virus impacts the dwarf gouramis, not thick lip/honey, at least last i checked it doesn't. The fish are young, it wouldn't be old age. And yeah copper would destroy my tank.
Symptoms are typically stop eating and two times fish got dropsy (different fish). No external things that say disease, i.e. sores

This happened to me with my Kribs. One day they just started bloating and gasping at the surface (slow progression) and dying. One by one. I had a thread on it Y’all are my only resource....Kanaplex for dropsy?! | Freshwater Fish Disease and Fish Health Forum | 477899
I treated with kanaplex as told after I think two fish died (maybe three I have to reread the thread) and then another was still sick so I did another round of kanaplex. Hope this helps!

Kanaplex has never worked for me, and the dropsy has only happened to the sunset gouramis, which is only 2 of the probably near 10 deaths over this span.
To clarify, last year a fish had a little accident with a piece of wood and got pop eye, tried to treat with kanamycin, did not work in the slighest, which makes me think the bacteria in my tank are kanamycin-resistant. Erythro did not work in combination with kana

 

Ok weird random things that can stress fish over time...

Stray voltage in tank? Do you every get small shocks when you stick hand in tank? Look up ways to test for this if not familiar.

Heavy metals in water? Ask LFS if they can test for this.

Expired fish food?

 

Ok weird random things that can stress fish over time...

Stray voltage in tank? Do you every get small shocks when you stick hand in tank? Look up ways to test for this if not familiar.

Heavy metals in water? Ask LFS if they can test for this.

Expired fish food?

I have never got any shock when I touch the water. As far as heavy metals, I thought prime dealt with those? I keep my fish food fresh, typically no older than 2 months and I get a new batch

 

How old is your aquarium equipment? My filter failed and killed a pygmy cory

 

How old is your aquarium equipment? My filter failed and killed a pygmy cory

Filters are still working although they are a few years old. Heaters are like a month old after my old ones were losing the ability to maintain temp

 

As far as heavy metals, I thought prime dealt with those?

Yes, at normal levels. Hopefully if you have city water that would all be in check. If you have a well, worth getting a double check.
Any tank bullies harassing fish relentlessly? Is the water flow ok for everyone?

 

Yes, at normal levels. Hopefully if you have city water that would all be in check. If you have a well, worth getting a double check.
Any tank bullies harassing fish relentlessly? Is the water flow ok for everyone?

I use city water. No tank bullies, just the occaisional apisto chasing fish away from the cave, but nothing persistent, I have a very tall piece of wood in the center of the tank so the flow gets interrupted by it but the flow works for aeration.

 

Heaters are like a month old after my old ones were losing the ability to maintain temp

Have you had any issues since heaters were replaced? Still could have maybe been an intermittent stray current issue from faulty heaters.

Have you had any issues since heaters were replaced? Still could have maybe been an intermittent stray current issue from faulty heaters.

Nvm, just reread. See you have new issues since then

 

Have you had any issues since heaters were replaced? Still could have maybe been an intermittent stray current issue from faulty heaters.

Nvm, just reread. See you have new issues since then

yeah I've had issues since then but it's just a continuation from the past 1.5 year that these fish have been dying

 

Could it be an oxygen depletion issue? This can happen in a heavily planted tank. How is surface agitation from the HOBs? Do you have any air stones?

Running out of ideas...

 

Could it be an oxygen depletion issue? This can happen in a heavily planted tank. How is surface agitation from the HOBs? Do you have any air stones?

Running out of ideas...

I've been through oxygen depletion before, the symptoms are a bit different and easily fixable with the air stone I have running. Plus, it wouldn't be killing gouramis which breathe air directly from the surface.
It is very frustrating. I might just go back to feeding solely flake & freeze dried food, maybe feeding the hikari frozen food is doing something, it's the only thing I can think of

 

Only thing else I can think of is share some pics of your tank, fish, substrate, etc to see if there are any clues there. Any signs of parasites? If you get all your fish from the same source maybe try a new store?

 

Only thing else I can think of is share some pics of your tank, fish, substrate, etc to see if there are any clues there. Any signs of parasites? If you get all your fish from the same source maybe try a new store?

I get them from several stores from the Baltimore/Philly/New Jersey area, I had that thought too unfortunately it wasn't it. The substrate is standard gravel, I can post my tank after I complete this water change but I don't think it'll offer any clues.

 

Sorry you are dealing with this mystery. If I were in your shoes I might try a UV sterilizer.

 

To get this out of the way, I have a 55 gallon tank with moderate stocking, 1 angelfish (her mate died a long time ago), 1 apisto mcmasteri, 2 honey gouramis, 1 sunset thick lip gourami, 12 x ray tetras, 12 cories, and 1 BN pleco. The nitrogenous wastes are 0 except for nitrate which varies from 5-10, my plant load and tons of water sprite keep that very low. So this issue is not a nitrogen cycle thing.
Over the past year and a half, very slowly, something has been killing my fish. First it was my peacock gudgeons so I've just given up trying to keep them. My gouramis typically die to dropsy, they just stop eating and blow up after a while. The fish usually die about 6 months after I originally introduce them to the tank after a 4 week quarantine. At first it was just gouramis and the gudgeons but over the past few months my tetras have started dying and my apisto hongsloi got really pale and croaked within a few days. The time this disease takes to kill varies from days to weeks, and just over the weekend I lost another tetra and my thick lip gourami is showing dropsy, but they were fine a few days ago.
This issue seems to be very persistent, and I'm getting really close to just giving up, I do my water changes and keep up with the work like I should but the fish just keep dying horrible deaths. Is there some bacteria just living the tank killing my fish? Is there anything I can do short of putting down all my fish and plants and blasting the tank and everything in it with methylene blue or something else to kill any bacteria?

I agree with sunflower430 - might be parasites, wouldn't hurt to deworm them.

However... I hate to say it, but this all really gives me mycobacterium marinum vibes... That 6 month incubation period was a major tip off, but the lethargy/sudden death is also a sign, often. I would recommend reading up on it. If it is, Clarithromycin is a go-to treatment for it, but Sulfaplex (Sulfathiozole) is another option, and easier to get. With either, it needs to be added to their food rather than just dosing the whole tank. Both need Seachem Focus to bind to the food, and garlic to be added to make it taste better. I *believe* that with both (definitely with the clarithromycin) that you need to keep them on that food for at least 6 months to fully treat it. I'm not the best with myco, so if you do think it may be that, I would recommend reaching out to "mycofish" on tiktok... I'm not sure what other platforms she's on but she's amazing.

 

I agree with sunflower430 - might be parasites, wouldn't hurt to deworm them.

However... I hate to say it, but this all really gives me mycobacterium marinum vibes... That 6 month incubation period was a major tip off, but the lethargy/sudden death is also a sign, often. I would recommend reading up on it. If it is, Clarithromycin is a go-to treatment for it, but Sulfaplex (Sulfathiozole) is another option, and easier to get. With either, it needs to be added to their food rather than just dosing the whole tank. Both need Seachem Focus to bind to the food, and garlic to be added to make it taste better. I *believe* that with both (definitely with the clarithromycin) that you need to keep them on that food for at least 6 months to fully treat it. I'm not the best with myco, so if you do think it may be that, I would recommend reaching out to "mycofish" on tiktok... I'm not sure what other platforms she's on but she's amazing.

Even if it's a myco infection, isn't that typically opportunistic? Which suggests there's some underlying issue allowing the bacteria to take hold. I don't doubt I have it in my tank somewhere, it's in 75%-ish of aquariums, but it shouldn't be an issue right?
I did deworm them a while ago with fenbendazole flakes, nothing improved.

Sorry you are dealing with this mystery. If I were in your shoes I might try a UV sterilizer.

I like that, would it harm my filter bacteria?

 

Even if it's a myco infection, isn't that typically opportunistic? Which suggests there's some underlying issue allowing the bacteria to take hold. I don't doubt I have it in my tank somewhere, it's in 75%-ish of aquariums, but it shouldn't be an issue right?
I did deworm them a while ago with fenbendazole flakes, nothing improved.

I like that, would it harm my filter bacteria?

No, It only sterilizes water in the water column. It should have no impact on the bb in your filter media or bb on surfaces

 

No, It only sterilizes water in the water column. It should have no impact on the bb in your filter media or bb on surfaces

Excellent, I'll look into that, I really think this is a bacterial issue. I took a bunch of other safeguards like running carbon in my media again on the off chance this is caused by some pollutant in the water.
Any recommendations?

 

Even if it's a myco infection, isn't that typically opportunistic? Which suggests there's some underlying issue allowing the bacteria to take hold. I don't doubt I have it in my tank somewhere, it's in 75%-ish of aquariums, but it shouldn't be an issue right?
I did deworm them a while ago with fenbendazole flakes, nothing improved.

I like that, would it harm my filter bacteria?

While many strains of mycobacterium are opportunistic, marinum isn’t really, though you do get more visible symptoms with weakened immune systems (and faster progression). When you get those sudden death from it, it’s because the immune system has been healthy enough to suppress it, but it does eventually overwhelm the system, causing that quick death with few symptoms. When that happens, it usually takes 6-8 months to overwhelm the immune system, which is why your note on that caught my attention.

 

While many strains of mycobacterium are opportunistic, marinum isn’t really, though you do get more visible symptoms with weakened immune systems (and faster progression). When you get those sudden death from it, it’s because the immune system has been healthy enough to suppress it, but it does eventually overwhelm the system, causing that quick death with few symptoms. When that happens, it usually takes 6-8 months to overwhelm the immune system, which is why your note on that caught my attention.

so if it's Marinum, I'm just screwed? I know mycobacteriums are very resistant to everything and reproduce slowly, so

 

so if it's Marinum, I'm just screwed? I know mycobacteriums are very resistant to everything and reproduce slowly, so

You could try the clarithromycin or sulfaplex as I described in my original post - they should work

 

You could try the clarithromycin or sulfaplex as I described in my original post - they should work

Wouldn't that also crash my cycle and don't you need to treat for months with multiple antibiotics to beat this?

Wouldn't that also crash my cycle and don't you need to treat for months with multiple antibiotics to beat this?

Looked into the sulfa one, what would the procedure be if I were to use it (it seems to be the most widely available of the two)
EDIT: and would UV sterilizer work against this? since it is so ubiquitous I feel like I'm just going to keep reintroducing the bacteria, but it may be better to just have sterilizer to kill it in the water
EDIT: and another quick thing, my angelfish, pleco, and catfish are all 3 years old, and don't have the disease. While my tetras are affected none of my catfish or their babies have ever got it. I've also given the babies away and none of the people I've given them to have had an outbreak of disease. My snails are also unaffected, they live out about 1-ish year lifespans unaffected

 

Wouldn't that also crash my cycle and don't you need to treat for months with multiple antibiotics to beat this?

Looked into the sulfa one, what would the procedure be if I were to use it (it seems to be the most widely available of the two)
EDIT: and would UV sterilizer work against this? since it is so ubiquitous I feel like I'm just going to keep reintroducing the bacteria, but it may be better to just have sterilizer to kill it in the water

Clarithromycin is a go-to treatment for it, but Sulfaplex (Sulfathiozole) is another option, and easier to get. With either, it needs to be added to their food rather than just dosing the whole tank. Both need Seachem Focus to bind to the food, and garlic to be added to make it taste better. I *believe* that with both (definitely with the clarithromycin) that you need to keep them on that food for at least 6 months to fully treat it. I'm not the best with myco, so if you do think it may be that, I would recommend reaching out to "mycofish" on tiktok... I'm not sure what other platforms she's on but she's amazing.

Clari works alone, but there’s only one site I know that sells it. As for crashing a cycle, I don’t believe it does.

tbh, I’m not 100% sure if UV kills it, but even if it does, it would only kill it in the water column, so you’d still need to treat the fish as they have large reservoirs of the bacteria inside them.

I really would reach out to Jane/Myco fish if you’re curious about more details. I’m not doing her work and knowledge justice here!

 

Well before you start dosing your fish for 6 months do try the uv steralizer. I had a similar problem a few years ago. Whatever it was picked off one fish at a time for about 3 months. I got the uv and havnt had a strange death since. I’m not a fan of medication. As much as it helps it also hurts the internal organs of the fish and reduces their life span. More fish die from the meds than are saved.

 

Well before you start dosing your fish for 6 months do try the uv steralizer. I had a similar problem a few years ago. Whatever it was picked off one fish at a time for about 3 months. I got the uv and havnt had a strange death since. I’m not a fan of medication. As much as it helps it also hurts the internal organs of the fish and reduces their life span. More fish die from the meds than are saved.

Yeah I've only had methylene blue + salt work in my 4 years of keeping fish haha i think I'm going with UV sterilizer to start and if the problem persists it's clarithromycin time.