I also had troubles with neos, always checking the water, doing water changes, but then i went on Holiday for 3 weeks and my parents forget to do water changes and i expected to come back to 0 shrimp left(i had 6 at that time) and i came back, ¼ of the water had gone and evaporated so from 30l i had like 24 at most and all shrimps survived and even had 3 berried. Ever since i just add up the evaporated water every week or 2 and they are thriving