Cory fishes not eating, swimming near surface

[Ersy]

Thank you so much for the answers and suggestions. A friend will help with re-homing the plecos and the loaches (I have 2 of them too...damn lady in the shop).

In the meantime, sorry to ask again but I am not sure what else to do. I did 3 good water changes and levels seem to be OK now (Nitrate is definitely under 20 and Nitrit zero, but I am still with the strip test as the local shop doesn't have a better one till next week). I decided to keep doing daily 10% water changes just to keep good water quality until I manage to give away the other fishes.

However, the corys are still behaving really strangely, although they left the water surface. 2 slept the whole day (and look like they are breathing heavily), one looks literally like a 'zombie' fish, spending all day swimming from up to down really slowly and heavily, yes lost and not eating anything, another one attempted to eat but still looks very strange.

My question is: could the suspected ammonia peak/or the use of the PhAcid have damaged them permanently (neurological damage)?
could they have some sort of infection (but I inspected them quite well and apart from looking increasingly thinner and breathing heavily, they look perfect)?

Is there anything else I could try to help them?

Thank you so much!!

 

[FishGuest5123]

Do you have a quarantine tank you can put them in until the other fish go? That way you can do daily water changes and watch . Cories don’t handle meds well so keep an eye on them. Have you looked at their bellies? Sometimes they get bacterial infections known as red spot there

 

[Ersy]

Thank you very much. No, unfortunately, I don't have a quarantine tank but I can keep doing 15-20% daily water changes in the main tank (I guess it wont harm).. their bellies look absolutely normal, as I cant see any red or any other colour spots anywhere..

 

[Ersy]

I have been watching the aquarium quite a bit today (and also gave away one of the plecos):

2 neon have fin rot (but they had this for months now without much change), and I think one of the harlequins has dropsy (very swollen belly and losing colour). some of the tetras have been 'flashing' so I suspect they might also have itch, I never saw them do this in the past weeks. clearly, I had really bad water quality, and a lot to learn.

the corys are still not eating and behaving really weirdly. water parameters are the same (so according to my kit they are fine, although PH on the high side), I also cleared again the filter.

I have the following options and I am not sure what to do

1. move the corys to another tank (with a friend that has a 300lt tank) and hope they recover there
2. treat the whole tank (itch treatment? esha2000?). I have a lot of newborn shrimps so I am scared they are going to suffer
3. just wait and let overstocking fix itself...

(I don't have a QT tank and to be honest don't have capacity to build one now)

Any suggestion?