Yes, I am having the same issue with my salt and pepper Cory's. I think it is some sort of bacterial disease. I put in a hospital tank as soon as I noticed them acting sluggish.. I put in erythromycin and with in 7 hours dead. Then the other started and I did the same and they all died within 24 hours29-gallon tank ammonia = 0ppm nitrite = 0ppm nitrate = 5-10ppm water changes: 20% weekly with vacuuming 2 angelfish, 4 platies, (used to be) 3 cories, 6 live plants temp 80 degrees I have two issues with my current 29-gallon tank. The first and more serious issue is with my cories. I cannot get them to live more than 3 or 4 months - I just lost my fourth batch (I always have between 2 and 3 cories and lose them all at the same time). They appear healthy; no visible signs of illness or infection and don't appear emaciated, but after a few months all of them get very sick, sluggish, and unable to stay upright (they act similar to fish with whirling disease). They die within 24 hours of the onset of symptoms. No other fish in the tank get sick. Has anyone ever had this phenomenon? Is it possible that they're not getting enough to eat? I put down an algae wafer once a week or so, and I always see them eating when I feed the rest of the tank. I don't vacuum under the driftwood; could there be gases down there that are killing them? Other possibilities could be that my nitrate kit is bad - I've never gotten a reading over 10ppm. But the plants are thriving and growing and the angelfish spawn every 12 days or so, which are all signs of a healthy, balanced tank. How would I be able to tell if I need a new nitrate kit? My other problem is with snails. I have both pond snails and Malaysian Trumpet snails. I've tried putting blanched lettuce in the tank at night, but the snails just snack on it and leave before I can collect any of them in the morning. I use my fish net to scoop out as many as possible, and I try not to over-feed so that they don't blossom. I still have way too many snails, though; they're great for cleaning up algae but they only add to the bio-load, and as mentioned above, I'm already concerned that my nitrates may be higher than they're registering. Would a dwarf puffer be a good idea? Are they even compatible with the fish I currently have? What do I do with it once I've gotten rid of my snails? Thanks so much!
I am expieriencing a similar problem with julii corys in a 29 gal with sand substrate, live plants, Ph7.4 ammonia 0 nitrites0 nitrates 10 with weekly 20 to 25 percent water changes. I have three that have been in the tank for well over a year but my efforts to add to that number have been largely a dissapointment. They do fine just as yours do for three to four months and then expire with little or no warning. The other tank occupants are eight baby angelfish that I am going to soon transfer to larger tank at home. Besides the flake food and occasional frozen blood worms that angelfish receive, I offer the corys frozen brine shrimp, shrimp pellets, and like you ,occasional algae wafers more for the malaysian trumpet snails than for the corys. I have bought corys from three different sources but still,, I have not had much success in maintaining a population of six. If i am ever able to identify possible cause ,Iwill gladly share with you what I have learned but as of yet, I am stumped. My 29 gal is filtered with Emperor 280 and has plenty of oxygen. Angelfish (babies) are doing well. Tank has been established for well over a year. I am near anal about water quality and cannot accept that possible enviornment problem is contributing to the demise of these fish. I shall keep searching for possible clue.:-(
