For the past two months my 30g. long has housed 7 rasbora espei's, 6 cory's (3 julii's and 3 panda's) and my beautiful male betta. In the past 4-5 days the cory's have not been coming out but hiding under the driftwood. I met with a new friend today who has run freshwater tanks and he watched my fish, trying to figure out was going on. Well, unbeknownst to me, the betta was starting to chase the cory's. I'm not sure how I missed this, but I did. :-[ A few days ago I moved my nano powerhead so as to create a bit more flow towards the plants. Very mild flow, but flow nonetheless. What we think happened is that due to the change in flow, the betta started working too hard to swim so he was resting more, and more towards the bottom where the cory's are. The betta didn't want to share space. It's weird because until a few days ago he would go down by them and everything was fine. So, today I went to WalMart and bought a really nice little 3g. cube with a small LED light. I also bought some black sand and a heater. I took 3 anubias from the 30g. and put them in the 3g. along with 2g. of water from the 30.; there is a VERY small filtration system. If a cycle does begin the plants will absorb the ammonia and nitrites so I'm not worried about my guy. I'll also be doing large water changes if I see anything bad beginning to happen. Interestingly, he appears to be swimming more peacefully (if that makes sense) and looks to be doing very well. And, the cory's are starting to come out and it's only been two hours since I moved the betta. I hope I did the right thing today and rectified my mistake. Rock and a hard place situation--damn I hate those. Wish my betta luck that I didn't mess this up.