Yer was thinking that because he swims in clear water it keeps it nice and clean without having to use dog shampoo and trying to lift him into the bath which is pretty impossible.

I've also been reading comments around the net with some people deworming their dogs every 3 months and some say that's a bit OTT and 6-8 months is fine, so I might do as you say, every 6 months.

How long would a 500mg of Bob martin worming tablets last?

Is that 1 dosage?

Thanks