Backyard Aquaponics
A place to discuss aquaponics

I've been doing aquaponics for 5 years but due too a leak I recently uncovered my FT to repair it. While it's been open and more visible I've noticed some of my Tilapia are hovering face pointed down with their bellies against the sides of the tank near the top of the water. I can only assume it's some kind of breeding ritual. Any thoughts?

Maybe the sudden and extra light hurts their eyes so they try to look down into the darkness.

With their bellies against the sides of the tank, I wonder could it be Ich?

Signs and symptoms
Typical behaviors of clinically infected fish include:

Anorexia (loss of appetite, refusing all food, with consequential wasting)
Rapid breathing
Hiding abnormally
Not schooling (in schooling fish)
Resting on the bottom
Flashing (Rubbing and scratching against objects)
Upside-down swimming near the surface

Interesting, I've never heard of this but if they aren't sick then it sounds like a defensive posture to me. Do they seem skittish? Notice any of the fish being aggressive?

Have you salted the water to help the fish with stress after you emptied the tank to fix it?

Yes, are they sluggish as well?

Thanks for all the responses. I didn't drain the water just transferred it to the sump so I'm using the same water with about 50 gallons top off. The fish aren't skiddish or moving around like scratching just staying in one spot. They have always swam near the top especially when the lid is open so don't think it's a light issue. One difference is I removed one side of the insulation so there is more light from the top to the bottom of the tank.

It still sounds defensive to me because they are so close to the side and pointed down, sort of an exposure issue. If something came over the edge of the tank where they were they are ready to head for the bottom and they are avoiding the center for whatever reason (light, aggressive fish...). Ask yourself what's different? Is there something in the tank that's really bright they are trying to avoid or would they just be out in the sunlight if they moved?