Over the past few days, I've mysteriously lost quite a few of my spotted rasboras (B. maculatus). From 11, I have just one left today.
Water parameters are good, but there is a new algae, I think staghorn unfortunately, and the other inhabitants are doing fine. Other inhabitants include 4 adult amanos and a couple of bee shrimps, and 3 danio erythromicrons. Tank is a 7g planted nano with an Eheim 2210 filter and lilys, with inline heater maintaining a temp of 72F.
It began a few days ago when I found four rasboras dried up outside of the tank, by the outlet filter. I gathered they had accidentally launched out of the tank as they liked to school together and these four were all together in a small pile as if they had launched at the same time, one after the other.
I made sure the lid was on after this point. Then, I lost three two days later. Couldn't find them outside the tank, but I did find one inside that looked like he recently died. This brought me down to four.
Today, there is just one. No signs of where the other two are.
I'm confused... if it's water parameters then why are the amanos and bee shrimp, or danios not affected?
I fed the shrimp some steamed zucchini twice this week outside their normal food, but again they are fine so not sure how it would have affected the rasboras.
Ideas on what could be wrong?