I agree with assassin snails. I had a huge snail invasion, and everyone said to get them, I did not listen and wasted money on loaches, that hardly made a dent on the snail number. There was so many snails that i could hardly see the gravel, and i aren't exaggerating, 3 assassin snails and 3 weeks later, and i can literally see no snails whatsoever. However i have now realised my assassins have gone on to eat each other now they are out of other snails