I stoped seeing my rasboras

[beastie]

Hi guys

I have a 60 liter cube tank, 40x40x40cm that I set up last summer. In November I added group of corydoras pygmeus, lost some, not sure what happened, not sure how many are left. In December I added 12 least rasboras, lost one. Took a month and they were comfortable, always at the front right space, active, not shy, not skittish. This is how the tank looked

 

Since then I had a hornwort meltdown, way more moss, some algae, and in March I have added two dario hysginon from another tank. They live mostly right back corner, center back corner, you can hardly see them unless food is involved. They are about the same size as the least rasboras, I saw no agrression towards any of the fish (neither in the other tank I have them in, they are not as aggressive as normal dario)

But since april I have not seen my rasboras. They all hang out in the left back corner, under the anubias, under the hornwort, they swim up front when they see food, but otherwise the tank is completely empty. If they were bullied by the darios I would suspect them hang out at the front where the darios are not. Since march I lost few pygmy corydoras that got stuck behind the filter on the right side and I also added an willow branch on the left and back side.

The tank looks like this now from the front

and from the right side

 

It has way more algae I know. Is it the dario? Something I did? I checked the temp on the right front side ( as heater is on the left back side) and teperatures match. I am sad, I miss my rasboras, they are super bright and lovely

Thanks, tips appreaciated

[epicene]

It's hard to tell if it's environmental stress or learned behaviour. I've had active swimming pygmies copy newly added skittish cpds resulting in everyone hiding in the corner. One runs, they all run. I'd start with eliminating lighting and shadow variables though. Block out three sides, dark room with just the tank light on, etc. see if they are more active.