Hello, fish community. I really could use some advice.
I have had this particular Tinfoil Barb for at least a year. I had two other tin foils, but both died, out of the blue, no symptoms.... just each died overnight, a few months apart, the last several months ago. I did get all three fish at the same time from the same shop.
My tank is 210 gallons, but it's really only filled to about 150 gallons. The main occupant is an African mud turtle, and she needs her sunning space. Other occupants besides Ruby and the tinfoil barb are random generations of guppies (all healthy), and a couple varieties of Tetras at any given time (also all healthy). I should point out that I really never have to deal with sicknesses in these small fish, since any under the weather individual is usually done in by Ruby during the first few nights of its illness. (This is probably not going over very well with you fish enthusiasts, and I do apologize if I offend, but I'm just giving the run down of the tank environment.) There are also usually a few mystery snails rambling around in there, but snails are a mainstay of the African mud turtle, so there is a fairly regular turnover of snail populations. Ruby is mega-destructive when it comes to plants, so all i have is a little forest of plastic plants, all of which have dark green algae on them. There is also a fine, healthy Gibbicep in the tank.
Ruby consistently leaves the large tinfoil barb and gibbicep completely alone. Even the two tinfoil barbs that died never showed the least damage caused by Ruby,neither pre nor post mortem.
The current water properties are (about) pH 7, alkalinity 120ppm, hardness 150ppm, nitrite >0.5ppm, nitrate 180ppm (yes, I said 180ppm, and yes, probably a problem, and yes, I blame my giant meat-eating turtle for this value, and yes, this is pretty standard for my tank), and chlorine just about 0ppm.
I have a Fluval FX5 filter, an inline UV filter, and an airline to keep things stirred up. The tank is generally kept at about 78 - 80oF, and is lit with two ReptiSun 7% UVB 96 watt lights, and 1 heat lamp.
Ruby gets fed a variety of things, most recently she's been on a super mealworm binge. My tinfoil barb is quick, quick, and will often steal at least two mealworms every feeding. Otherwise the fish get mostly TetraMin flakes and occasionally frozen cubes of glassworms or bloodworms.
Okay, that's the big environmental picture and life history of my tank.
On to my fish. My lovely little tinfoil barb has a big red lump on its lower jaw. Now, it's been there for a while, this tiny little red speck that you could barely see, and half the time I thought I was imagining it. I mean that. I wasn't sure I was seeing anything really amiss. Bu then, I just went away for a week, and I came back, and...BLAM! ginormous lump. I've only been home a day, but other than the lump and the fact that it's out in the open and not lurking in Ruby's cave (as is more normal), the tinfoil is looking rather okay. It is eating flakes, but I haven't tried a worm yet. It isn't especially fretful or agitated, lethargic or lopsided. It just has that awful lump. The white little bits you see on/around the lump - I think that is the fraying epidermal layer, not something like a fungus.
What do I do? How to I help my last barb?