Rosy tetra with hole in the belly       8/24/18
Hi,
I was wondering if you could help me.
<Sure thing.>
I have a 25 liters fish tank in which I've been housing 2 females lf rosy tetra for the last 3 years.
<These are nice, usually unproblematic tetras.>
Fish keeping is not my priority but I've been regularly changing 25-50% of the water and tried to keep the tank relatively comfortable for these 2 fish to live.
<Understood. However, 25 litres is much, much too small for these fish.
It's barely adequate even for a single Betta. It would also explain your problem.>
A couple of months ago one of them developed a black round dot on it's belly around the anal area.
<Yes; possibly a wound, but hard to say at this point.>
That dot has slowly grown larger and yesterday I noticed it looked like she had cotton on the dot. Well today the "cotton"-like fluff disappeared but she has a massive dent/hole on her belly.
<I can see this, yes. The white stuff coming out from the wound is dead tissue, likely muscle and skin tissue. It's what we'd call an infected ulcer in the case of a human, and while the cause is hard to pin down, it's evidently infected with bacteria that are causing the wound to explain (and preventing it from healing).>
She acts normal and eats normal however the wound doesn't look all right at all.
<I'll say!>
I was wondering if you would happen to know what this is and if there is a way for me to help her at all?
<Two steps. Firstly, a bigger world with better water quality. With the best of intentions, as I'm sure you have just reading this message, 25 litres is, what, 6 or 7 US gallons? For this species you'd really need at
least 2-3 times that amount of water to be considering this a "healthy" environment. Too little water means too many bacteria, and too little water also means too little dilution of metabolic wastes. Regular water changes help, for sure, but realistically you'd need to be changing the water every day or two simply to create conditions similar to, say, a 60-75 litre/15-20 US gallon tank that received water changes every week or two. There's just no sense to that amount of work, especially if fishkeeping is a casual
hobby. Put another way, the less work you want to do, the bigger your tank needs to be. The smaller the tank, the harder work it'll be, and ultimately more expensive once you factor in dead/replacement fish and medications.
Now, the second thing to do is treat as per Finrot. Again, let me stress here that medications are like sticking plasters -- they're fine once the injury is done, but if the patient keeps sticking knives in themselves, plasters aren't going to help! Similarly, if the water conditions don't improve, you'll be repeating the medication again and again because the bacteria will keep coming back. Aeromonas and Pseudomonas spores are everywhere, and you really can't keep them out of the tank any more than you can live your own life germ-free. Can I also add that medications vary in quality. The tea-tree oil ones are generally cheap but unreliable, so avoid. Salt is equally worthless, though often recommended to inexperienced hobbyists. Instead look at a proper antibiotic (if available in your country from a pet store) such as Maracyn 2 or Kanaplex, or else a trusted antibacterial like eSHa 2000 or Waterlife Myxazin.>
Please see some photos attached
Kind regards, Anda
<Hope that this helps. Cheers, Neale.>