I am new to the tropical scene, but unexpectedly faced this issue recently.
I have a 130 litre (34 gallon) tropical tank filled with the following:
3 bristlenose
4 danio (leopard and zebra)
3 opaline gourami
2 pakistani loach
1 male ramirezi
4 rosy barb
1 golden severum
3 shark (1 albino, 1 rainbow, 1 silver)
2 golden sucker fish
4 congo tetra (2 male, 2 female)
4 neon tetra
4 glowlight tetra
I had a female betta in a small bowl so my children had a fish they could feed a set amount to in the morning while I fed the fish in the main tank. Unfortunately for the bowl, a child under two came to visit and got hold of the edge of the bowl. Faced with the choice of betta in the community tank or betta on a wooden floor, I chose the tank.
Inside the tank I have two mid/large anubias barteri on a log and two rocks - one natural, one fake but designed to look natural. The log has several hiding places, including (as I found with the betta) a hollow area for her to hide in. She has now been living in the tank for ten days. For the first few days, I barely saw her. I'm presuming the bowl I had her in was the largest thing she had ever been in, and faced with a large swimming area and a total lack of "alone time" had her nervous as heck. However, she has been getting quite adventurous in recent days, to the point where she is no longer racing into her hollow log, and is coming up when I put my hand in the tank. She and the ramirezi seem to have made a decision that the area both fish preferred is now hers, and he is finding new territory to keep busy in. She has now established her territory between the fake rock and the anubias foliage, using mostly the rock for cover.
I am in the process of organising to get a larger tank, and I'm considering moving the more aggressive (and more energetic) fish like the rosy barbs and congo tetras into that tank. Especially since one of my male congos has an aggressive streak, and evidently has a dislike for neons (any time we get more than four neons, he kills off the extra). He has never tried to kill any of the other fish, even the glowlight tetras, although he does exert his territory, which is a small open section of the tank, which the betta avoids as there is no available cover that high up.
