Re: White Cloud Minnow Blackened Tail, White lump, fast breathing
#3
Thanks very much for the helpful description and accompanying photos.
I don't think this is one that is easy to diagnose and/or it is beyond my experience.
I have had these types of scenarios before but have always had several ongoing theories as to what they might be.
For example, in your case, it looks as though there might be a growth or even ?fracture/injury at the leading age of the anal fin (may have occurred in the frenzy for food or sparring with another fish, or may be an internal growth), which might very well account for the blackening and buoyancy going awry. The lifting scales, if localised to the site of the bend, are more likely because of it rather than dropsy which tends to be all over. The round white lump on the dorsal fin might be another growth, or it might be that something internal is causing all of this, and the hyperventilation a consequence of the stress on the fish.
When I have situations such as this, I usually have the dilemma over whether to isolate in a hospital tank (if I think it's communicable) and chance a treatment such as eSHa 2000 in case it's an internal bacterial infection, or keep monitoring the situation and hoping that more regular water changes and some sort of 'tonic' that doesn't affect the other fish might help (personally, I like Melafix in such situations, but I know others don't). Some of my fish have been ok with isolation, others get more stressed and I've returned them to the main tank before dosing the medication.
In your case, fortunately this holding container suggests that yours is ok with isolation, so you could put it in a hospital tank with filter (containing filter media from the current filter) to treat. Another option (and *especially* if you don't have an additional tank with filter which the fish would need) is a small breeding box for use in the main tank which enables closer monitoring of it and might be less stressful for it if not being cascaded around the tank or investigated/poked at by curious tankmates - either a collapsible/stowable 'mesh incubator' or an 'acrylic isolation box' (which I would think would be ideal for your situation).
Hope this helps somewhat.
[NB. Ensure that water quality is optimum at all times too - 0 ammonia, 0 nitrites (and <20 nitrates if at all possible, or no more than 20 above whatever your tap water reading is).]