I kept a fish alive in a 5 gal of bucket, with some crabs and snails, and even a cleaner shrimp for 6 weeks. The bucket only had 3 gals of water in it too, and I thought he died after about 2 weeks, and slowed down the feedings to 2x a week or so (for the cleaning crew), and I was surprised to find him alive when my tank was rebuilt.