I had a pair of kribs in my 20 gallon with guppies. There were no problems between the kribs and guppies or plants but the female krib didn't last long. She spawned once because I now have several (or more as the tank is heavily planted and they move fast) 1/2" long baby kribs, but then she died. I did see the male chase her a few times, so I'm afraid he may have harassed her to her death. They are a neat fish and I'm glad I bought them, I just wish it hadn't cost the female her life.