I have some new corys purchased in February. They were quarantined for 4-5 weeks (rather than 2 weeks) as two had some fin issues. They were resolved without treatment, just extra water changes.
Now the cory below and one other of it’s shoal has the marks underneath pictured here. Very hard to get pictures, taken so many and this is the best one. Is this bacterial?
I removed some fish in January due to worms. They had only been in the tank a few weeks, max 6, were treated in another tank 3 x ndx and esha 2000, and then returned to the shop. No evidence of worms in other fish so waited a month before getting the corys and then quaranted them 4-5 weeks.
I’ve been given very mixed advise. I am inclined not to treat the tank for worms as it spreads it, and for it to spread I would have needed for the dead fish to have been eaten. The fish was not eaten, but one eye was missing.
I am now concerned that if this could be more than bacteria. Originally thought ammonia but no evidence of ammonia found, and don’t use ferts so no ammonium unless Prime is interfering. Cory still active and eating.
I am an experienced fish keeper with platys and top level shoalers etc but I just had a 2ft tank until recently. New to catfish, keyholes etc.
Ammonia and nitrite 0 Nitrates 25 post water change and 35 ish pre water change. Tap nitrates 30 Ph 7.6 Gh 14 Kh 10
These parameters consistently using 1/3 RO water. Unipac aquarium silver sand for the corys.
200 litre tank with 2 young keyholes, 6 baby corys, 1 bristlenose 3.5 inches, 5 platys, 11 emerald eyespot rasbora (platys and rasbora going in own tank when sure all healthy).
Do I need to deworm all fish? What with? Probably nematode worms based on recent reviews of shop. Should I remove the sand that was there when there were worms? How should I treat the corys?
Any other advise or guidance welcome and appreciated.
That does look like a bacterial infection so I would treat with eSHa 2000 or Myxazin. If you see no evidence of worms I wouldn't treat. There's no need to change the sand, but if you find they do have worms and treat, syphon the entire surface to pick up any expelled worms from the sand.
Keyholes re usually pretty laid back as cichlids go, so I'm wondering if the cory has some fin rot going on, especially as he has suffered barbel erosion too, which is often bacterial. If you treat the tank with the Myxazin that may sort this out too. If it does turn out that your keyholes are too aggressive then their own tank will be the answer. The plan you have in mind will work, but the 60 will be heavily stocked so may need more/larger water changes.