When do betta fry grow their ventral fins?

Hello,

Just wondering when a betta fry grows its ventral fins? As a teen I used to breed bettas (but wasn’t very good at it and didn’t have a lot of success). Now, a decade later, I am older (and hopefully wiser) and have decided to try breeding bettas again.

I spawned my marble plakats on Aug. 21, and the eggs hatched on the 22nd. They have been doing really great, growing fast. There are about 80 fry. However, I’ve heard that sometimes betta fry don’t grow their ventral fins for an unknown reason (possibly related to microworms or water quality) and I’ve been anxiously watching my fry daily to see whether I can spot any ventral fins. They are almost 3 weeks old, about 1 cm long, and all their other fins have grown... but I took some photos a magnifying glass and still don’t see any ventrals. Should I be worried? Or is it too early for ventral fins?

They are in a 10 gallon tank. Starting right at the free swimming stage, I have been doing a 50% water change every 48 hrs, including siphoning all the scum off the bottom and occassionally scrubbing the bottom/walls of the tank with a sponge. There are some live plants and a sponge filter in the tank. Ammonia and nitrites are 0, nitrates around 5-10 ppm. I had a bit of an ammonia spike at 1 week old, but I did an immediate water change and added some nutrafin cycle and it has been stable ever since. I fed microworms for the first 5 days, then fed a mix of microworms and bbs daily for the next five days, then fed exclusively bbs. Today I started introducing grindal worms along with the bbs.

I hope it’s just too early and that they will develop healthy ventral fins soon!

@Crispii

Theyre splendens but you have betta raising experience


I raise sparkling gourami and I didnt notice their pelvic fins for a long while because theyre so small its hard to see. Plus they like to keep them tucked up against their belly a lot too.

While I have successfully bred Bettas, I have not yet bred your typical Betta splendens. Instead, I actually bred Betta imbellis, a close relative of Betta splendens. From what I observed, I noticed that my Betta fry actually started to grow their ventral fins at the 6th or 7th week.

Thanks for the replies! Crispii, that’s really good to hear! Mybe it’s still too early for them to show up at this age. Mine aren’t quite 3 weeks yet.