I was really surprised by how easy it was for my king to acclimate with all the other fish. Such an easy going fellow!
There's a happy ending in the works; but it definitely took some effort to get there.
The 12 gallon test did not succeed. My king betta was perfectly happy with the other inhabitants, and I had brought in his cave, and added a lot more fake plants to change the scenery- but it was the flame gourami male that jinxed the happy home idea - when he went into attack mode both times he swam into range of the betta.
And my poor Arthur, each time, made a hasty retreat. So I put the plastic cup into the tank and Arthur swam right into it! That's how happy he was to be leaving the 12 gallon.
The happy ending is that I next took him to the big tank - I'd spent a few hours before that to finish planting the 30 gallon with the clippings that had just arrived in the mail. I brought Arthur's cave and put it at the bottom beside several of the other caves there. And, after a little while of having the other fish checking out the cup and the smaller fish not even bothering to check it out... I released him ... He, at first, didn't want to leave the cup.
But I gave him a minute or so and a little bit of pushing, and he made his way into the tank and all the activity. He discovered the floating plants and hid for a bit. He swam to the bottom and was very shyly hugging to the sides of the buddha head, and the other caves, trying to stay hidden...
He didn't like it when my Goldie (girl juv. gourami) came over with her feelers, but she was not aggressive with him, and didn't pester him too much. He got a similar 'meeting' from Pearl and her feelers - and then they left him alone - It was at least 2 hours before he felt comfortable to swim fully around the tank without 'looking' over his shoulder.
I went to bed at 2:30 last night, and he was enjoying the space by that point. And this am when I checked on him he was swimming, swimming, swimming around the tank, figure 8's, playing in the current from the filter, and the lower power-head - seeming to really enjoy himself. Occasionally, he crossed paths with the gouramis and was already acting relaxed with them. And, the Pearl was interested enough in his 'tactics' that she spent some time imitating him and his mirror/glass shimmies. :)
Success! A happy home for King Betta with a Gold and Pearl Gouramis (Girls), 2 Boesemani rainbows (boy/girl), 7 threadfin Rainbows, 7 Neon Tetras, 2 Cardinal Tetras, 3 Albino Cories, and 1 mystery livebearer (I'm really thinking it's an endler).
I may need to make space in the tank as some of the inhabitants grow to their more adult sizes. In a few months I'll consider moving the tetras into the 12 gallon tank with the Meany Flame gourami and Serpaes. But for now - what an exciting community tank! Such a pleasure to watch them all. :)
All's well that ends well.