Pangasius Fish Acting Strange

[FoxRaid]

I have had this pangasius for about a year now. He has been living in a 125 when I had first got him. I decided to change him over to a different tank since he has got big, to our 300g tank. This new tank has 2 grouamis and a Bala shark in it. I added the pangasius and at first he was okay for about a week then when I got home from work one day he was white as a ghost. I was worried something was wrong with the water so I did a water change I checked the water and nothing was wrong at all. I waited a day to see if things would change and nothing did. I ended up moving him back into the 125 with fish I had him with when he was a baby. Odd enough they are community fish and he has not Eatin a single one or has made any attempt to. As soon as he was in his old tank his color changed back to normal after a few mins and he was swimming calmly around the tank. Can anyone explain why this is and is this just a common thing?

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[Caliban07]

I can only think of 3 things.

1) he was being bullied when you wasn't looking.

2) something about the positioning of the 300 was stressing him, extra noise, vibrations, light.

3) he was home sick. You had him in the 125 since he was a baby with other fish and now he is out of his comfort zone.

Pangasius are the most easily scared and skittish fish I've come across.

 

[FoxRaid]

It's probably the last one because my 300 I have underwater filters so it's quiet and my airpumps are on the other side of the room so not much vibration going on that he can hear. How can I adjust him to the tank, should I add some of the other fish he swims with in the tank. I don't have alot of fish in that tank yet but my 125 I was planning to move some of the fish in there since I've suddenly gotten overstocked since I took my friends fish. I just don't get why he rather be in the crowded tank then one he has room in.

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[Caliban07]

Did you drip acclimate him properly?

He may just take some time to adjust and would probably ok after a week or 2. It's just that he may be open to opportunistic disease if his immune system is lowered due to stress.

Is the ph/tds the same in both tanks?