Basic Pond Fish Needs

Basic Pond Fish Needs

A Big Aquarium

It is best to think of pond fish in the same way that one would think of fish in an aquarium. Both are in a synthetic environment that is on a closed circuit, meaning the same water is simply recycled within a designated area. There are a number of important things a pond owner must do to sustain fish in an unnatural environment.


The first major item is filtration. As in the aquaria hobby, filters often dictate success in one aquarium and failure in others. Every pond needs biological filtration because fish waste does not magically disappear or float downstream! When we say this, we don't mean the foam strainer that protects the entry to the pond pump or the sand/gravel in the bottom of a pond. What we mean is some sort of storehouse of bacteria that has exposure to flowing water in an attempt to balance it.

If this balance does not take place, a buildup of organic debris collects and the pond could experience a spike in ammonia. This is not good for the pond fish because high levels of ammonia are what typically will cause an aquarium to crash and can severely damage even the hardiest of fish.


The process of adding a biological filter in most ponds is too often overlooked and for ponds that containing fish, it is a critical one. A good bio-filter is capable of both mechanical and biological filtration. What we mean by this is the filter is able to catch the big stuff (i.e. leaves, seed pods) and on a bacterial level attack the organic waste emitted both by decaying matter and fish waste.

The biological portion of a filter is created by adding loose material that has a large amount of surface area. This area is then inhabited by lots of bacteria, just like bio-filters in aquariums.

Pond bio-filters often come two ways, either internal or external. Zamzows sells both! An internal filter is good for those ponds that are smaller than 500 - 1000 gallons. They are pre-pump so that the water passes through the filter prior to the pump. They contain levels of foam media (mechanical) and a chamber of bio-media (biological).

For those who have larger ponds, there are advanced external filters. These pond filters operate with gravity and are usually placed where the water pours out after being pumped out of the pond. In most cases the water comes in the back portion of the external filter from the pump, then passes through a level of mechanical filtration, and is exposed to the bio-media before it pours out.

Zamzows carries several variations of the external filter, each with its own benefits based on the type of pond they are used in. It is critical to mention at this juncture that it is never a good idea to clean out a bio-filter! Removing debris from the mechanical portions of these filters is a good idea periodically, but removing and scrubbing out all media will result in an immediate pond imbalance by killing all the good bacteria that have accumulated. Also for those who live in a climate were winters with killing frost occur, the bacteria that live in ponds die. In early spring it is a good idea to purchase bio-filter booster, bacteria in a bottle, to instantly colonize a bio-filter and get that water clean!

Oxygen is Key

Another key item for fish is breathing! Aerating your pond via air stones or the good old fashion way of using a waterfall will help out your fish greatly. When the water from a waterfall slams into the surface of a pool of water, it helps to oxygenate it, giving the fish an abundant oxygen supply. For those who live in colder climates, during the deep freezes of winter, make sure that the pond never completely freezes over. When this occurs, carbon dioxide is trapped in the pond and oxygen is trapped out. Specially designed pond heaters will help to maintain a hole in the ice, allowing this gas exchange to occur.

Since the pond environment is simulated, it is also a good idea to provide sources of food for the fish. It is true the goldfish and koi will sometimes feed on plant material like the roots of floating plants or algae, this is not a good diet for them long term. Pond fish are usually bought for their brilliant colors (a result of genetic mutations!) and the way that you keep your pond fish noticeable is to feed them a generous diet of protein! Pond fish food is designed just for this and it also adjusts with the seasons. When the temperature in a pond cools, the fish experience a slowing in their metabolism; as a result they don't receive hefty feedings of protein very well. Spring and autumn diets are available as are summer diets to adjust to the needs of the fish.

Give them Shelter

For those who live in areas where natural predators exist (blue heron, raccoon, dogs, cats, snakes, and the like), providing areas for fish to hide is a good idea. Hollow pavers and cinder block are easy ways to provide adequate cover for fish. Pond plants with large foliage also help with this problem, like pond lilies and floating plants.

Adding Pond Salt

Finally, the addition of salt is very beneficial to pond fish. When added salt helps to attack parasites and also provides the fish with valuable electrolytes. When adding salt it is important to dose it correctly. Too much can kill the plants and fish in a pond. When purchasing pond salt make sure to follow the application instructions.

Much like fish in an aquarium, pond fish live in the same sort of conditions. There are a few critical things that must be supplied in a man-made environment. By supplying a few items, pond fish can and will thrive. After all, koi can live to be 50 years old when kept healthy!