The biggest single threat suggested by many to pondkeeping from the natural world is the heron. 

 Some others are cats , snakes , racoons among others. 

We all love herons when we see them swoop majestically down on to the lake and wait statue like for the next meal to swim by.

But when the victim is your prized fish that cost you hard earned cash or you raised it from fry is hard to swallow , if you excuse the phrase.

Lets look at it from the herons perspective , you are flying at 100ft see a crystal clear pond full of brightly coloured fish in shallow water. Do you fly on to the murky 1,000,000 gallon lake or stop for lunch.

Understand your enemy

Likes to feed alone

Does not like to step over things

Prefers shallow open water

Predator Prevention Aids

Herons are protected by law so all measures taken must have the welfare of the bird in mind.

Decoy Heron

Widely used and readily availble from retailers. Simply works by the flying heron sees another heron already at the pond site so keeps flying.

Works best if moved around the pondsite to make it seem lifelike. 

Plus point; is easy to install , minus point; is can attract herons in the springtime looking for a mate.

Passive Infra Red Scarer 

Works in the same manner as a PIR outside light , as you approach the light it comes on or in the case the water comes on.

It spreads a blanket passive infra red over the pond site and if anything breaks the blanket shield ie a Heron it emits a blast of water as a deterrent.

Plus point helps against cats and other predators that walk to the pond. Minus point; requires batteries or mains power and a source of water. Also remember to approach it from behind or you will get wet as well.

Netting 

The most effective method and also helps against falling leaves must be a fine net. Plus point; very effective and shades pond as well. Minus point; you can not enjoy your pond.

Lifelike Snake 

Place a lifelike snake on a rock near the ponds edge , Plus point; Inexpensive. Minus point; no real experience of effectivness and may scare relatives who work up to the pond.

Fishing Line           

Place a ring of fing line 12 inches from the pond and 6 inches high. Idea is the heron will not step over it.

Plus point;inexpensive and not unsightly . Minus point; Trip hazard and not 100% effective.