At what age betta fry show their full developed fins?

[Aniket]

My fry are now showing anal fin and few of them showing colours. There are fry on size basis 30% bigger, 50% medium, 20% smaller. At what age fry will show all developed fins?

 

[Colin_T]

It takes about 12 months before the males have full sized fins. They get most of the fin size between 6-9 months but they continue to develop until they are about 1 year old.

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The different sized young are normally caused by lack of food. The male fry have bigger mouths and get more food and grow faster. The females and mutated fish that don't swim as well, get less food and don't grow as fast.

Make sure you feed them at least 3 times per day and do lots of water changes to keep the water clean.

 

[Aniket]

Why water change is necessary for betta fry?

 

[Colin_T]

If the tank has an established filter running on it, the water changes keep the nitrates down.
If the tank does not have a filter then water changes will dilute ammonia caused by the fish food and waste.

Water changes and gravel cleans remove fish poop and dilute disease organisms in the water.

All fish fry grow faster when given regular water changes. It's my opinion that fish fry produce hormones that inhibit the growth of other fry around them and the water changes dilute these hormones and allow more even growth.

 

[NickAu]

Why water change is necessary for betta fry?

For the same reason water changes are necessary for adult fish.

 

[Demeter32]

Trust us when we say more frequent water changes are a must. The fry grow much faster with daily water changes and frequent feedings.

As for when you start seeing nice fins, it takes a while. Depends on how fast the fry are growing but right around and inch long is when you should be able to sex them. My fry are around 5-6 months old and the males are finally starting to fill out and build little bubble nests.