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Strange Growth on Neon Green Tetra

Chris C.

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Hey all,


We have a 15 gallon tank with 13 Neon Green Tetras and 3 Male Guppies. We've got a Vallisneria plant, a Cryptocoyne Parva plant, a Java Fern, and some Java Moss in the tank.

Chlorine Level: None

Nitrites: None

Nitrates: between 0 and 5ppm (closer to 5 than 0)

pH: 8.2 (which is a bit high, but that's been the stable reading for our tank for months)

Ammonia: None

Temperature: Between 78-79 Fahrenheit (Pretty consistent)


We did a 25% water change (gravel vacc'ed and cleared some algae from the front and sides of the tank so that we could see the little guys) on Sunday and discovered a weird bump on one of the tetras on Monday during feeding. It's up near the front of the fish, sort of under the mouth. The tetra still appears to be swimming fine, came up to feed with no problems, and otherwise appears to be behaving normally.

It took a while to get some decent pictures, but see the attached photos for the bump.












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Wow, that's actually kind of a big bump! I was expecting something smaller when you described it. I want to say it's a tumor, which is something you can't really treat, but let's hear what others have to say. I'm trying to think of what else it could be... an abcess maybe, (which would be bacterial.) Or some weird parasite, multiplying in a pocket of the fish's skin? 

Let's get some more opinions.

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My husband said he's spotted it on another fish. From what I've found online now about Dermosporidia/Dermocystidium (thoughts seem to be split about whether or not it is a fungus or a parasite or some strange combination of both) there's no real cure, just closely monitor and keep fish healthy and low stress. I'll keep an eye on them and post occasional updates.

Since there have been no behavior changes we're thinking we won't medicate. If anyone else has any ideas of what it might be, please share!

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Looks like the original one passed sometime between yesterday and this morning (found that one stuck behind the sponge on the filter nozzle just now). There's one more with it. We're considering euthanizing that one to protect the remaining population. Thoughts? Suggestions? Dermosporidium/Dermocystidium don't really seem to have cures, and they're not supposed to be particularly deadly, but we don't want to lose any more fish.

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Unfortunately we can't have a good QT set up in our apartment. It's really confusing that this is coming up at all. The last things we introduced to the tank were the tetras, 2 guppies, a java fern, and a java moss ball in early August after the LFS QT'ed them for us for 2 weeks for an extra fee. We've had no problems with the tetras since then. One problem with one of the guppies we'd had before that in October, and one guppy who over ate a freeze dried food and had swim bladder problems in early November, but nothing like this. Seems like a long time for something to lay dormant.

I'm honestly not sure if we're just doing something wrong at this point... The water parameters are always fine...

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Well, the second tetra was having a lot of trouble swimming today. The tetra was floating vertically at times and hanging out at the bottom of the tank for a while, but occasionally swimming around fairly normally (usually only when disturbed by us or another fish). We opted to cull it as humanely as possible, given that we didn't want the little one to suffer.

Not sure if the blob was causing breathing problems or swim bladder problems (given the vertical floating).

As far as we can tell, none of the other fish are showing signs of the blob of doom (as I've decided to call it).

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