Lump on Danios Side - a repeatedly unanswered question

One of my fish has had a lump on her side for about 6 months and the other has had it about 4 months. I originally thought it was a tumor of some kind, and since it doesn't bother the fish at all, I haven't done anything about it. These fish are all two years old.

I have found several threads asking very similar questions, several on this forum, and several which never received any replies at all. The most closely related is here.

I don't have any older pictures to show growth over time, but these lumps have been growing at a constant slow rate at about the same speed on both fish. I don't know how quickly the lump developed at first (could have been overnight, could have been over the course of a month) because the coloration and location made it difficult to see.

I apologize for how dark the photos are. It's hard to get brighter pictures that aren't blurry. I tried to get pictures from both the side and the front for both fish.




As you can see, the Gold Longfin Danio has a much larger growth with several smaller lumps further down her body. The Leopard Longfin Danio has a smaller lump that is almost pointy from certain angles. They are entirely internal and grow slowly enough that they never rupture the skin.

The lumps haven't been affected by water changes, moving three times, or raising catfish fry and danio fry in the same aquarium. Both fish act completely normal. They are active, interact with the other fish, and eat normally. All the other fish are also fine and don't have growths.

Has anyone ever seen this in their danios (even if you never found a cause)? Anyone have any ideas as to what it could be? Does anyone know if the problems are related or if it's just a coincidence that both fish have similar looking problems?

Some more info about the tank:
Size: 10 gallons + 1 gallon refugium (for fry)
Fish: 2 longfin leopard danios, 3 longfin gold danios, 4 peppered cory catfish, 1 julii cory catfish, 9 gold danio fry and lots of juvenile peppered cory catfish. I'm moving most of the fish to a 29 gallon as soon as the pH stabilizes in the new tank.
Temperature: 78F
Plants: one small java fern

My guess would be some kind of tumour but I supose the worrying thing is how is that happening to multiple fish?

Are you able to get a water report at all from your local supplier? You can ususally get them from their website. Do you know how the water is fed into your house? I'm wondering if you have lead pipes or some kind of contaminent that is causing this?

Just anecdotally, we had a member many years ago who lived near the M1 in the UK, her garden more a less backed onto it. Her whole neighbourhood had horrific air pollution and a people that lived near her developed types of lung cancer, animals like cats and dogs were getting ill too and she was finding that some of her fish (she mainly kept big cichlids and catfish) were developing tumours too.

Failing something envrionmentally, either in the water or air like the above. The one disease that comes to mind is lymphocystitis. It usually presents its self as an external disease with white growths on the fish but it can develop internally as well, usually alongside external symptoms but not unimaginable. If it were some kind of virus it would explain why more than 1 fish has developed the growth.

Lastly did both fish come from the same place?

Wills

The water idea is interesting. Over the summer I brought my aquarium to a lake. The tap water there is pumped straight from the lake, fed through a good mechanical filter, and then through a UV light to sterilize it. My cory catfish loved the water and were laying eggs every three or four days. Since I was interested in raising some fry and since the fish seemed to enjoy the lake water, I used empty seltzer and tonic bottles to store enough water for 3 months of water changes. I monitored the water carefully to make sure it wasn't growing bacteria or changing in any way. The only change I found was the pH dropping, but it would quickly go back up with a little aeration. I finally ran out maybe a month ago. From recent tests in the lake, I know that the area where the water is pumped from the lake is very clean. I also find it unlikely that anything alive got to the tap, but maybe it's possible?

Both the fish came from LiveAquaria, which isn't known for the highest quality fish. It's likely that they are already somewhat inbred. I lost several danio fry early on due to clear inbreeding issues and one of my danio fry stopped growing at about a quarter inch long, despite having a healthy appetite.

Its not the biological content of the water I'm concerned about its the lead and other heavy metals that can cause tumors I'm concerned about.

The other thing I've been thinking about tonight is Iridovirus. In 2 ways, initally I was wondering if we are starting to see a new disease in Danio stock like we started seeing a few years ago in Dwarf Gourami. But then when I started searching some of the pictures of Dwarf Gourami with Iridovirus look quite similar to your Danio. Multiple species can catch this virus so wondering if it could be that? Just in a species not commonly associated with it?

Wills

It's either tumours, cysts, an internal infection (Fish TB?) or parasitic worms. Most likely tumours or Fish TB.

There's nothing you can do about it. Just monitor the fish and if they have trouble swimming, eating or do stringy white poop, then euthanise them. Other than that, leave them.

In a way I hope it is a tumor or cyst because at least then it isn't contagious. I'm hesitant to keep the danio fry with the adults if it is contagious. They currently share the same water but have no direct contact.

Instances of fish tb in betas look very similar to what my danios have. I had three or four of fifteen danio fry die early on. Within 24 hours, they would develop a 90 degree curve in their spine and sink to the bottom of the breeder box. I assumed it was genetic, since curved spines are common genetic deformities. Could it have been fish tb? What would that mean for the rest of my fish?

For anyone who comes across this thread, this page has interesting info on how common tb is and general info on tb.

What I'm not sure about is how hard I should be trying to prevent the spread of tb, assuming the fish even have it. It sounds like fish can recover from tb. Can I ever again assume my tank is "clean"? Considering 40-80% of fish stores have strains of tb, is it even worth doing anything differently (other than a few precautions to make sure I don't catch it from my fish)?

If I move any of the fish with no symptoms or direct contact to my new aquarium, do I have to assume the aquarium is now contaminated? I made a 3D background for it that would be very difficult if not impossible to sterilize. Would I need to avoid adding new fish in the future?

Considering I haven't anything new to the aquarium other than UV sterilized water for more than a year, is it even possible that they have tb?

Fish TB doesn't kill fish in 24 hours and doesn't cause the spine to curve in 24 hours. The bacteria are really slow growing and it takes months for any sort of change to become noticeable in fish, and that is assuming the granuloma (TB infection) is even near the spine. If it's not near the spine it won't affect the spine.

There is no cure for Fish TB.

There should be a few articles on this forum about it because I have written about it before.

If one fish has TB, then every tank at your house will have it. Just assume it's a tumour and get on with your life. There's no point stressing over it unless you want to get the fish necropsied by a fish vet. That will confirm one way or the other if it is TB.

Until then, just wash your hands with warm soapy water after working in the tank. And don't put your hands or arms in the tank if you have any open wounds, cuts, sores on them because you can develop a localised TB infection in the wound.