I have a tank with gravel substrate. I really want some kuhlI loaches but they can only live in sand as I have researched. Should I change all my substrate to sand or change half of it to sand? I would really like some kuhlI loaches but i'm not sure which I should do for them. Also how would I proceed in doing so if I don't have a quarantine tank for my DG in the meantime as I do the swap of switching my substrate. Should I really perform this switch I'm afraid it'll mess up my tank but I really want my kuhlI loaches what should I do?