ammonia in crayfish new setup

[finfayce]

hi- it’s been awhile. i can’t add the App. ?
i have started a crayfish tank recently. ammonia level is one level below zero. maby water changes but can you di too many water changes.
to my horror. the first crayfish - i must have moved somethisomething because it died from a broken pincher. but a nerite snail died same day.
have been using API ammo loc. i have a new crayfish. he had a molt yesterday. how soon should i wait before another water change?