Peppered Cory With Red Line

[BBrain]

Tank size: 27 US gal.
pH: 7.5
ammonia: 0 (total NH3+4 0.3 ppm)
nitrite: 0
nitrate: 1 ppm
kH: about 4 dH (80 ppm)
gH: about 4 dH (75 ppm)
tank temp: 26.5 C (79 F)

Fish Symptoms:
Bright red line on rear of left side, below lateral line, along edge of one armour plate....just appeared this morning. Behaviour is normal. All other fish look okay.

Volume and Frequency of water changes: 2 or 3 US gals. about twice per week.

Chemical Additives or Media in your tank:
Five "Flourish Tabs" put in gravel 2 weeks ago, plus 2ml "Flourish" liquid being added once or twice per week, in past 2 weeks.

Recent Medications:
Has been 1 week since completion of 5-day Maracyn (erythromycin) treatment, concurrently with Quick Cure (mainly formalin, some malachite green) treatment at half-strength as per manufacturer's instructions for scaleless fishes.

Tank inhabitants: 6 Lemon Tetras, 3 small Peppered Corys, 9 small Glowlight Tetras, one Otocinclus.

Thanks in advance for any suggestions!
Photo:

 

[WILDER]

Does it look like a tear as though he caught himself on something sharp.

 

[BBrain]

At first glance, it looked like a sharp cut, like from a knife or something. But I can't think of what object in the tank could do that. Cories have sharp pectoral fin spines, so perhaps one of the other cories slashed him with a spine.

Here's another theory: Perhaps, in his busy swimming, he caught the edge of an armour plate against an object, like the wood in the tank. That might have caused the plate to be pulled enough to break some blood vessels under the plate. Is that possible?

In any case, I sure hope he will heal on his own. I don't want to subject my tank to a new round of antibiotics, and risk the biofilter bacteria again.

 

[WILDER]

Bless him, maybe just add some melafix, just make sure the wound dosn't get infected, good luck.

 

[BBrain]

I was thinking of trying Melafix. I've never used that stuff, but on your recommendation, I'll get some for my medicine cabinet.

Okay, now for some good news! This morning there is no sign at all of the red slash! It's as if it was never even there! I'm so relieved, but now here's another mystery to me!

As far as prevention goes, if he got a skin plate caught on the edge of a wood piece, I can't do anything about that, I guess, because I like that wood a lot. But, I think I'll remove one piece of rock that has some harsh-looking edges, in case he was injured by that. I like rounded rocks better, anyway.

Thanks for your help again, Wilder!

 

[WILDER]

Just get some sand paper and rub the sharp edges down, that all i do., then rinse well.

 

[BBrain]

Good idea with the sandpaper. Thanks!

This cory, and at least one other cory as well, have been flashing on pieces of wood, the last couple of days. So I think my injured one may caught a skin plate edge while doing this. I guess their skin is a bit irritated from the recent medicine. But other than the flashing, they look fine, and they're still busy little eaters!

 

[WILDER]

Just keep an eye on them, yes meds can irratate there skin, good luck.