Why do you want to use the tsp as it just the same as melafix.
Not sure of the ingredients in tsp.
You can use diluted methylene blue you just dab the area with cotton wool.
I can't bear to use TCP on myself let alone even contemplate using it on a fish. Evil stuff and can be smelt for years after use and it includes a mixture of phenol and halogenated phenols.
probably originally injury but its been 4 weeks and its just getting worse so i'm sure it must be infected. When it 1st happened I treated with melafix, it started clearing up but didn't heal, I then tried protozin which had no effect. Then I tried an internal bacterial med and it's just getting worse so i've gone back to melafix. just gettin desperate to find something to help him!