3 is ok
deflection is how much glass will bend
looking at a guys tank the other day
asked him if he was worried about the 4mm deflection on top of his rimless tank
the answer was hadn't noticed it before
IF YOU MEAN mebendazole
it is available in the wormer vermox
but copper sulphate will do the job
but dead bodies will pollute the tank water if you have a lot of snails