Metal does not tolerate long-term submersion in water. It's normal for any type of metal fastener, filtration equipment or decoration that you place in your pond to begin to rust after it's been in the water for a while. Rust doesn't benefit the fish in your pond in any way, however -- rust should be kept out of the pond water whenever possible.
Metal poisoning can occur when fish are exposed to metals within their living environment. Metal poisoning is the result of fish being exposed to higher levels of metal than their bodies can naturally filter back out. Fish with metal poisoning may appear ill. You may become very ill if you attempt to catch and eat fish that have been exposed to metal and are suffering from metal poisoning.
Rust in Your Pond
Rust can enter your pond due to rusting pipes that deliver water to your reservoir or as a result of metal objects being placed in the pond. A small amount of rust in a large pond may not cause any problems, but if you want to protect your fish from metal poisoning, you should make sure you have done everything possible to keep metal that might rust out of your pond. The type of metal and the length of time it remains in the water will determine the amount of rust you ultimately wind up with in your pond.
Metal Poisoning Signs
Metal poisoning is very difficult to diagnose, but fish who are suffering from it may have cloudy eyes, appear to be gasping for breath, change color or even die suddenly. Visible rust or discoloration of the water can also be a sign that there's too much metal in the water.
Safe Pond Decor
Always choose pond decorations and equipment that have been designed to be safe in water and safe for fish. If you see rust in your pond, locate the source and remove it from the pond. You should also regularly test the water quality in your pond and treat it as necessary to keep the water safe for your fish.