Hi, i recently helped set up a large tank for a friend, we bought all the fish from the same shop and no issues up until recently, there are approx 100-150 small snail like creatures in the tank (possibly snails hehe), on the glass, on the plastic plants, on the filter and when i looked closely they take up most of the gravel on the bottom ....there are way too many to take them out by hand, can anyone advise on the best way to resolve this ....Whether it be a poison or a fish that will eat the snails, thanks.