I recently purchased 15 new fish for my 20 gallon aquarium, 4 boraras maculatus, and 11 boraras uropthalmoides.
These fish looked great, and settled down quite well, but I quickly noticed a change.
Initially, both the boraras uropthalmoides and the boraras maculatus seemed like very happy, very active fish.
They stuck together in schools, occasionally mingling, with the maculatus staying towards the surface of the front, with no apparent fear of humans, and the uropthalmoides, hanging in the lower parts of the aquarium, a little more timid but still active.
All were feeding readily, and exploring all areas of the tank.
After about a week, I began to notice spawning behaviour in the uropthalmoides, but then a couple of days later, it was as if they had all disappeared.
The maculatus are still very visible and enjoying the front of the tank, but the uropthalmoides now continuously hide in the back of the tank under the plants for what seems like basically all day and all night!
I don't know what's wrong with them. I feed microworms in the hope that they'll be found by the uropthalmoides in the back of the tank because they no longer come out into the open to feed!
Why are these fish so timid???
I've attached a photo of the tank, and the corner in which they like to hide underneath the hydrocotyle, remaining stock still if you approach in any way.