New Pygmy Cories are pale and breathing heavily

I got 2 new pygmy cories two days ago (to add to my existing 3). The first day everything went well--new and old cories played and sat together, and the new guys started sifting through the sand after a couple hours.

Yesterday, the new cories mostly sat in corners of the tank separately from each other and the old cories. In addition, the old cories were less active than usual and would be startled (like really flip out) if I so much as got out of my desk chair three feet from the tank. The 3 old cories were thriving before I added the 2 new ones.

Today, new fish are still sitting in opposite corners, are pale, and are breathing heavily. They have not eaten. I see no other external signs or flashing. They barely move, but when they move they seem to writhe more than swim. Old fish are slightly more active than yesterday but still not normal and didn't eat much. Water test today indicates normal parameters (0/0/5).

Any ideas? Maybe the new guys just need time to acclimate, but I'm afraid I bought sick fish. I don't have a QT or hospital tank. I do have Kanaplex if it's useful.

 

Don’t medicate yet. Clean water is key. Do a 50 percent water change. Do you have an airstone? Cories especially need more oxygen in the water than others. I have encountered this before (the paleness and heavy breathing) however that was due to high nitrites.

 

Thanks. I don't have an airstone but can get one easily enough. (Although they 3 were fine before without one?) I'll try the water change.

 

Thanks. I don't have an airstone but can get one easily enough. (Although they 3 were fine before without one?) I'll try the water change.

Good. Never hurts to be safe.

 

One of these new fish looks really bad. Turning almost white, and he was just swimming (for the first time today) all along the surface of the water as if he's in need of oxygen. I am changing the water now and will get an airstone tonight, but I'm concerned... The other one seems a little better.

 

I am so sorry, but all of my cories that have had those symptoms passed away shortly after.