I'm thinking of swapping out Eco complete for a sand to be better for my corydoras. Are there any fine sands that have a high or moderate CEC? If not, are there any high CEC materials that could go under the sand but wouldn't need replacing like soil would? Would relatively hard clay balls work well under sand?
Forgive my ignorance, but why is the change better for your cory's? Could you put a sand cap on the Eco-complete? As was previously mentioned, sand has little (if any) CEC.