A drop per gallon of Aquarisol is an excellent preventive for all kinds of nasty stuff that your bettas can get. Before I started using Aquarisol, my 1 gal. betta bowls would still get nasty even with very frequent water changes. This has become part of my water-changing routine, and my fish are staying healthy and happy. Great product. Can't get it in our local fish stores here. Great price. One bottle of this stuff will last you forever!