Terrific. I love the idea of having lots of tail variety in sorority tanks. It gives you lots of breeding options going forward and is a good study for betta knowledge. The Hornwart is an good plant for betta but goes through different stages. If the pieces you have are under decent light they should grow. Often ive had hornwart go through a shedding of its blades stage. When that happens break off the dying piece but save the green ends. It should go into a grow phase again thats when you can take lots of pieces for other tanks jars ect. I have never studied much about hornwart so a good google would have better info than Ive provided lol.
Crazy thing, we put Smokey in my empty 10g after you left. He is a panda marble ie black and white. Up till 8 weeks he was super colorful and lost all color like Finnigan. Today he is turning a sky blue color in only a few hours. His color gene turned back on. I hope Finnigans does too. The speed of the return shocks me the most. Family just left now I can try some photos. Oh how I wish I had taken a class in photography, betta are the hardest thing I have ever tried to photograph arggh.
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