New quarantine tank

[PAULZER055]

Hello everyone,

I just set up a 10 gallon quarantine tank (QT).  The water cycled, 0 ammonia & 0 nitrite, water temp 78 degrees.  I lost most of my fish in one of my tanks awhile back, the reason I set up a QT, so I decided to use the preventative medication treatment recommended by Aquarium Co-Op, Paracleanse, Maracyn & Ich-X.  Yesterday, I put 3 Paleatus Cory’s in the QT and this morning, when I checked on them, 2 were floating, upside down, at the top of the tank.  I got a net to get them out and when the net touched them, they both scurried to the bottom of the tank.  Later this afternoon I checked again and the same thing happened, 2 floating upside down and raced to the bottom when I touched them.  Any idea of what’s going on?  If they are dying, anything I can do to help them?  Thanks for any advice you may have.

[Cinnebuns]

2 things come to mind:

1.  When you say "water cycled" it's important to know that you don't cycle the water but the filter, glass, substrate, etc. Bacteria does not live in the water but on surfaces. Also, what is your nitrate levels? 

2.  This is a behavior in cories that may indicate self poisoning. At any point were they kept in a small container? How big is the tank they are currently in?  When stressed cories will release a poison. If they are in a small area it ends up poisoning themselves. 

Either way I would do a water change and check the nitrates. 

Edit: I reread that it's a 10 gal. That's large enough for what they are in but still if you kept them in a smaller container before the 10 gal it could be the cause. 

Edited August 15, 2022 by Cinnebuns

[PAULZER055]

Thanks for your response.  I do understand about the beneficial bacteria being on surfaces and not in the water.  The QT has a sponge filter, heater, a cave and some fake flowers that can be used to hide in.  No substrate just a bare bottom.  I can check the nitrate level later this evening.  I did notice the filter has a lot of debris on it in the form of old food.  I tried to get the ammonia level up by ghost feeding until I found out about a product called fishless fuel, which I ended up using along with some liquid beneficial bacteria.  Think I should rinse sponge filter off?  I bought the fish from a pet store and I think the use 10 gallon aquariums for their fish.