Slugs in up stairs toilet cistern

That's caused by built up of mould and lack of usages.

To eliminate slugs, you will need to find out how they are getting into your property. One way to do this is to use a torch to illuminate a slug trail and follow it to its entry point.

It is worth noting first that slug pellets have been banned in the UK because of the risk to other wildlife and pets.

Next, you want to block their entrance. You can use a draught excluder for gaps under doorways or filler for holes in walls. Slugs can get in even tiny cracks, so ensure you fill them all well.

You will have more of a problem if they are using a vent, as you will be unable to block the route in.

Fortunately, some alternative methods can discourage slugs from entering your home.

Copper Tape
Gardeners have been using copper tape around their plant pots for years because it gives off a small charge when touched by slugs. It causes no harm, but slugs do not like it and usually stay away.

You could protect vents and other necessary openings with copper tape.

Salt
Salt has also been used for years by experienced gardeners. It works by rapidly dehydrating the slugs causing a quick death.

Dr Gordon Port from Science Focus refers to salt as “kryptonite for slugs”.

One problem with using salt is that it needs to be on a dry surface and away from soil that will be contaminated.

Deal with Damp
As slugs are drawn to damp, dark places, it is sensible to ensure that any dampness in your home is dealt with promptly.

It would be best if you wiped away any condensation on windows to discourage slugs from entering.

Encourage Predators
What better way to keep slugs away than to let nature take of them?

There are many natural predators for slugs, including birds, frogs and hedgehogs.

You can encourage birds into your garden by providing food and water. A bird table or hanging feeders make attractive additions to your garden.

A wildlife-friendly pond will encourage frogs, who are also rather fond of slugs.

Another creature that loves some slugs is a hedgehog. You can install a hedgehog house and create hedgehog holes in your fence to encourage their passage through your garden.

Keeping on top of your slug population in your garden by creating biodiversity will reduce the risk of slugs coming inside.