Lost fry and tank re-start

Sadly I lost the fry two days ago. I took out all the sand from the bottom so to see better whether there is lots of debris on it to be cleaned out and it will be easier to spot the small fry.
Tank No.1 male and female HM
She is the floating tank at the left and he got a noce big plastic cup to build a big nest this time. I will release her today to see if they will breed. Tank No.2
Male HM and female CT. She is in the breeding net box to the left. I released her yesterday into the main space to see wheather they will breed. He is chasing her and she is swimming away. Today I will give her brake for 3-4 days and see if there are any fry in the nest before I release her again.
As one can see I am using much less water this time so male can see the fry much easier if they drop out of the nest. With time I will increase the water depth.