How long before I can leave rainbow fry with no food for a few days?

[Coryloach]

I am really glad your fry did well.

I personally always have an empty tank running, which some call it quarantine tanks but mine are always setup with sand, hardy plants and cherry shrimp. When I buy fish or I have fry to move on, I use that tank. Established tanks are the best quarantine and fry tanks for many reasons. Cherry shrimp are a great cleaner crew alongside peaceful fish and a good snack for more predatory fish.

 

[joe jaskot]

One of the best things to have in a fry tank is java moss. Plenty of microscopic organisms for fry to feed on.

 

[Cardeater]

Just an update. I like to update bc I find it frustrating when I find threads during searches and no follow ups.

I now see this fry would definitely be fine. Fish was bigger than rummynose tetra in June and is close to being bigger than my female praecox rainbows. It seems obvious that fish would be fine in Oct.

Not the best pic but the "fry" is the fish on the top: