What Should I Do?

[stanleo]

I finished my fish less cycle on Thursday, did a 65% WC. 55gl tank. I added 10 flame tetras, 14 harlequins, 12 corys on Friday. 9 of the harlequins, 6 of the corys came from Petsmart, the rest from Petco. When I bought the harlequins from Petsmart I noticed that some of them had torn up and missing fins. There was nothing else noticeable wrong so bought all of them. I shouldn't have but I did. On Saturday, I bought an angel. I have lost 5 of the harlequins. They get dull in color, then get lethargic, then can't swim well, then die. None of the other fish are showing symptoms, they all seem really healthy, for now. There is one harlequin that is lethargic and two that are dull in color. I bought Melafix and started treatment today and I am feeding a high protein diet. I have been tested every 12 hours since putting the fish in and have had now spikes in ammonia or nitrite. PH is stable at 7.6 and GH is 120ppm.

I figure I have 2 options. Go through the treatment see if the three get better or go ahead and euthanize them. What would you do? What do you think they have?

 

[stanleo]

And another one. I'm taking out the sick ones and treating the tank with a stronger antibiotic.

 

[Mamashack]

When I did my fishless cycle I had to do a 90% water change to reduce the nitrates to a reasonable level. Did you check the nitrates after doing your 65% one? Maybe they were still a bit high. Also in the past I've found angel fish to be anything but angelic and in fact quite aggressive at times. Maybe it was stressing your harlequins?

Did you mean GH 120 or 12?

 

[stanleo]

My nitrates were reduced to 20ppm and I meant 120 for GH. I lost 2 by the time the angel was introduced.