i have had a costomer come in everyday for the last week. he has 12 2g betta bowls each with one betta, an apple snail, and some have ghost shrimp. he has brought one of his snails in with a white hairy looking slime covering it. he says a few of his bettas have caught this and died. he described the fish as "wearing a white fur coat." never seen this stuff before. sorry no pictures. anyone know what it may be and how to treat it?