So I have 15 CPD (which I bought off the aquarium ads forum here hehe) and they adapted very well to my newly set up planted tank. 3 weeks in, they were beginning to get less and less shy, and although shying away from me when I approached the tank, they quickly came out and were very active after that. When I put the algae wafers in the tank for my 6 other cories, they would swarm around and eat little specks that the cories missed.
However, all of a sudden, they are now very shy and this change was very sudden. They (as usual) shy away when I approach the tank but this time most of them don't come back out, even if I sit still for about 45 seconds. This poses a feeding problem, as they dont come out to eat whenever I drop food into the tank, and once the food hits the bottom, they refuse to touch it, and this leads to fouled water and hungry fish.
Could there be any explanation for this sudden behavior change? I know they get stressed out by my High-lumen light when its on, cos they're more active when I turn it off, so Im planning to get some duckweed for my tank. Its a 20 gallon high planted tank and I didnt change any part of my feeding/applying ferts schedule.
The only major change was that I removed a large internal filter because the current it created was too strong. However, there was no immediate change again.
PS, should I add dither-fish eg endlers?