Achilles and Powder Blue behavior - Lights on vs. off

[tbone28]

I've had a PBT in my 180g for a few years now. Added an achilles a couple months back from reefhotspot.com. Both fish are similar-sized. Achilles is eating and doing fine.

My PBT is the tank's boss. When the tank lights come on, my achilles stays on the right side of the tank. If he swims over to the left side, the PBT will chase him back over to the right side. edit: they don't fight. The achilles doesn't fight back. So long as he swims back over, the PBT will move on.

The weird part is when the tank lights are off. My achilles swims around freely in the tank, and my PBT lets him. My achilles will swim right in front of the PBT, and the PBT doesnt care. Even with my window shades open and thus letting in a lot of natural light into the room, the PBT lets the achilles do as he pleases. It isn't until the tank lights come on that the PBT wants the achilles over on the right side of the tank.

Any thoughts on why this happens?

 

[sohalfr]

I've got almost the same behaviour between my hippo tang and my blue ring angel.

When main lights are on, the hippo tang forces the blue ring to stay on the left part of the tank. No real fight but sometimes high pressure.
Under blue lights or when all lights are off, the blue ring can swim around freely in the tank.

 

[tbone28]

Weird huh?

 

[Allmost]

maybe they get lonely at night ?



lol joking, I have no Idea, but most fish calm down ALOT after the lights are off.

Except Eels

 

[tbone28]

Would some time spent for the PBT in the sump do anything to change this behavior when lights are on?

And regarding calming down when the lights are off: Even with a lot of ambient light from the windows, the PBT is calm. The PBT distinguishes between natural light and tank lighting?

 

[kirkaz]

IDK, but if you have a Powder Blue and Achilles in the same 180 without them killing each other, be thankful.

I will say this about lights, any time I try to just have my "lunar" lights on, my Sohal becomes very nasty, I don't do it at all anymore....Either all lights on or none on.

 

[sandwi54]

IDK, but if you have a Powder Blue and Achilles in the same 180 without them killing each other, be thankful.

I will say this about lights, any time I try to just have my "lunar" lights on, my Sohal becomes very nasty, I don't do it at all anymore....Either all lights on or none on.

+1. Just be glad that the two arcanthurus aren't killing each other right now. however, when they mature and "perceive" that the available space decreases, things typically change. not saying that's what will happen for you, but it has happened to many.

what is happening now is that the PBT has claimed the left side of the tank as its territory, so when the achillies comes over it's being perceived as territory violation. if you want to change this situation, i would remove the PBT for a couple of weeks and rearrange the rocks. put it back and see what happens. PBT is generally more aggressive than achillies, so it's better to let the achillies stake out its territory first. this way when the PBT goes in it would learn to share the territory with the achillies. of course, each fish has a different personality so i can't speak for every one of them, but this is what i've observed from my experience.

 

[tbone28]

My question doesn't lie with the PBT "owning" the left side of the tank. As stated in my original post, he's the boss. My question is why this behavior doesn't happen with tank lights off. The tank itself can be well lit with light from the windows; yet, the PBT is mellow