So here is another update on my rhomboid- the acclimation box is out, i also decided to do some rock rearrangement, nothing drastic, but something i had been putting off anyway, with hopes that it would diffuse any aggression.
There hasn't been any noted aggression at all. The rhomboid is very wary of the pintail, and avoids it still, but no chasing nothing.
I had initially worried about it, not because i had witnessed too much aggression, but because the rhomboid liked to swim near the surface so much, but now that it has been in the tank for a few days, it has become clear, that the fish is just a bit odd.
Even when the lights are off and no other fish are around and it is clearly not stressed, (no gasping, no other signs of stress etc), it just likes to cruise near the top of tank. It doesn't always stay there, and it does go near the bottom corners and when feeding will go wherever there is food. TBC it is not swimming at powerheads or anything.
The only other odd thing to note, is that the fish rarely hides or full on sleeps, lights on or off. Again, it seems to be doing well, but it appears to be up at all hours even when the rest of hte fish are asleep. Not sure why.