New pond - fish acting strange

[Kslemar]

I’ve recently built a 14000 litre pond from a 2500 litre pond. I have 5 small koi, 1 medium koi a Sterlet and small sturgeon.
The Sterlet and sturgeon loved the big pond at the start but recently are staying under the water fall along with the big koi.
It’s been a real pain getting the greedy koi not to eat the Sterlet and sturgeons food, the big koi seems to swim at these fish all the time. Water levels have been checked and showing all fine

 

[j.w]

@Kslemar

 

[Kslemar]

View attachment 128664@Kslemar

Thank you!

 

[Mmathis]

Hello and welcome!

 

[Kslemar]

Hello and welcome!

Hello thank you

 

[addy1]

Welcome to our forum!
Post a picture of your setup when you can.

 

[Phaewryn]

recently are staying under the water fall along with the big koi.

They may be hiding from predators. Do you have a net over the pond? Can you put out a motion sensor camera to see if there are predatory birds coming to the pond when you're not looking? It could also be lack of oxygen. Do you have aerators, a fountain, or is the waterfall current strong enough or enough of a drop to create oxygenation? Pics would help.