Ok first I'd like to start by saying I know I'm going to catch a lot of heat for this post but please don't be too harsh. About 3 weeks ago I brought home 2 kribensis to put in my 45g community tank. My local petco ordered them just for me. I was there when they received the shipment. They received 3 and one was DOA. The other 2 were not looking so good and 1 of them was in very bad shape. I told her I wanted them both so I could hopefully nurse them back to health. She only charged me for 1, because we both were sure the other wouldn't make it. I had a coupon and paid $1 for them. I brought them home and after I acclimated them they were both very stressed, at the bottom of the tank and I thought I would lose them both. The one that was worse off, lived for about 12 hrs. The other at one point I really thought I was going to loose. Super stressed, at the bottom, lathargic and not eating. He also had torn fins and a huge chunk of his tail missing. I put some seachem stress guard in the tank daily and his fins and tail started growing back. He slowly started being less stressed and more active. He was very peaceful at first. But then he seemed stressed again and started going after my platies. I think he may have killed 2 of them but not positive. I couldn't risk keeping him in there. I took my baby betta out of his tank and put a divider in my adult bettas tank. I ended up putting my kribensis in the 5.5g tank. I put in a cave for him and it has a few silk plants, and a moss ball and an aquaclear filter. I told myself it was just temporary until I figured out what I should do with him and my platies. But I love all my fish and didn't want to give up any of them. I thought my kribensis would be super stressed in a much smaller tank but he's the total opposite. He loves his 5.5g. He's not stressed at all, eats better, loves exploring the tank, loves his cave. I've never seen him so happy. My 45g had tons of hides, very large silk plants, driftwood, floating plants and live a u bias and moss balls. I do plan on upgrading him to a 10g soon but isn't it odd for a fish to prefer a small tank?