What would cause platy fry to grow slowly?

[Runsoncoffee]

I have 7 baby platies in a 5 gallon tank. All of my adults are in a larger tank, so it’s only the babies in the 5 gallon. It’s been several months and they are still under half an inch. I’ve been feeding them more frequently and changing the water more often, but it hasn’t changed much. What would cause them to grow so slowly when they have adequate room?

 

[Dallascowboys16]

I have 7 baby platies in a 5 gallon tank. All of my adults are in a larger tank, so it’s only the babies in the 5 gallon. It’s been several months and they are still under half an inch. I’ve been feeding them more frequently and changing the water more often, but it hasn’t changed much. What would cause them to grow so slowly when they have adequate room?

Baby fish grow out slower in smaller tanks. That is just how it is. I have read some papers stating that fish produce a growth inhibiting hormone which, when in small spaces, can cause slow growth. Typically the bigger the growout tank the better. That plus frequent small feedings of a variety of foods and clean water will grow fry faster.

 

[Aiken Drum]

That's correct on the growth hormone. If fish are kept in too small a space, or when water conditions are poor, fish put a hormone into the water that stunts growth. Its whats responsible for stunting goldfish in bowls for instance.

Regular water changes can remove this hormone and help. Ive seen instances where fish that grow large can be kept in very small tanks and grow to full adult size if they are fed a constant supply of fresh water and the hormone is never allowed to build. There are obviously other health and ethical issues involved in this. I dont know this is the case, but i assume extensive fish farming must do something like this.