Neudorff Fast Acting Slug & Snail Killer Ultra

Neudorff Sluggo Fast Acting, Organic Slug & Snail Killer Ultra 500g

Covering double the area that regular Sluggo does, the active ingredient is 20 g/kg hydrated ferric phosphate (equivalent to approximately 14.02 g/kg anhydrous ferric phosphate), a naturally occurring iron compound. It is completely effective against all species of slugs and snails (not insects).

• No slime trials, no visible dead slugs.
• Unique micro pellets are both ideal against juvenile slugs and snails in early spring, and allow greater coverage with the same amount compared to normal pellets.
• Extremely resistant to rain.
• Certified organic.
• Biodegrades into useful nutrients for plants.

Application:

• Scatter 2.5 g/m² evenly: never apply in mounds or rings around specific plants
• No waiting time before harvest.
• Apply in the evening when your intended prey is most active
• If an infestation is severe, apply to areas surrounding the area you want to protect as well, so that there is no escape...
• Do not apply more than 4 times per crop

Do natural slug repellant methods work?

Generally, no.

Eggshells or coffee grounds are useless, and copper bands are merely a nuisance to a large slug unless you connect the copper band to a battery to make a weak electric current.
Salt kills slugs, but it's bad for your soil and quickly stops being effective with rain. Diatomaceous earth is harmless to soil and to slugs: in dry weather (when slugs generally are not much of a problem) or locations, it is an effective repellant, but as soon as it gets damp it stops working.
Beer traps will, depending on their design, catch a certain percentage of the slugs that visit for a drink, but most of them have a free sip and escape. 

Slugs have population booms in places where their predators are absent. Slug eating birds need nesting sites like hedges, and toads and beetles like to hide under the same pieces of dead wood and other debris that harbour slugs.
Slugs are everywhere, so every pile of rotting logs is home to them, but many urban gardens have no toads around and a low beetle population, and therefore not much incentive to create homes intended for those slug predators, which end up full of slugs instead.
In the countryside, however, you should find that piles of logs and some rocks around your garden will encourage toads and beetles to settle in and help to keep the slug numbers low. 

The balance of nature theory: Most slugs prefer to eat recently dead or diseased leaves, rather than fresh ones. By keeping your soil "messy" and covered in leaf debris, you provide slugs with their favourite food. The theory goes that if there are enough predators around, they will feed well, and the surviving slugs will focus on the rotting leaves lying on the ground, not your tender plants.
In practice, it rarely goes that way, so be ready to enforce some serious "balance" with your Neudorff Sluggo!