If you got male and female fish from the same shop or even from a different shop within a month of each other, they are probably related. Most fish that come into the country come from the same suppliers in Asia and most if not all the shops in your town will be getting fish from them.
You breed whichever fish are nice and healthy and look good. If you mix up bloodlines it will usually give you healthier young, but it also undoes the work that has been put in by the original breeders. That is to say people have been line breeding Bettas to make bigger fins, round tails, unusual colours, etc. If you breed a short fin with a long fin or a yellow fish with a blue fish, you will get fish that could be yellow, blue or a different colour and have short, medium or long fins.
Most purists will say only breed halfmoons with halfmoons, and short fin with short fin, blue fish with blue fish, etc, but the choice is yours. However, if you produce ugly, deformed or short finned fish, they won't sell as readily and you could be stuck with hundreds or even thousands of young fish and nowhere to keep them.
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As long as the tail and fins do not become infected, 2 weeks should be adequate.
I hope the Gambusia (mosquito fish) have been removed?
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You can put 4 females with the male (not the other way because the male has his territory and needs his bubblenest before he breeds) but watch them all closely and see which one he prefers. Once he has picked a partner remove the others. And watch the females in case they decide to gang up on him.
One way to introduce female Bettas to a male is to have the females in tanks next to the male so he can see them. Watch the fish and see which female the male spends most of his time showing off to and use her for breeding.
You can do the same thing with breeding nets that you hang inside the male's aquarium. Each female gets put into a breeding net and you monitor the fish and see which one the male prefers. You should also watch the females to make sure they respond to the male. If the female isn't interested the male might bash her.
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You start feeding the fry as soon as they become free swimming.
The eggs hatch after a few days and the fry either get put back in the nest by the male or they stick to the glass or plants. A few days later they start swimming around just underneath the surface and this is when you start feeding them.
Make sure you have a cover on top of the tank to keep the air above the water warm for the fry.
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We need pictures of the fish if you ask that type of question
Red Bettas and Blue Bettas are the most commonly sold. Ask your local pet shop which ones sell best because they will be the place buying them from you.
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Just treat all of your fish with Praziquantel (at the same time) to get rid of gill flukes and tapeworm. Treat them once a week for 3 treatments. Do the same with Levamisole (but on different days) to get rid of round/ thread worms.
Do a 75% water change 24 hours after treating them, and remove carbon from filters so it doesn't absorb the medication.