This is not as much of a how to use but how long to use. I've finally started using indian almond leaves, and I've put a leaf in my 5.5 gallon betta tank. It's now been about a week, the leaf has sank, and has started growing black spots. Should I still keep the leaf in there, or should I remove it? Will it change the water pH or anything if I let it decompose? I don't have any shrimp.