Is My Pond Ready for Fish?

Choosing fish for your garden pond is more than just finding a species or variety you like. There are many factors you want to consider before buying a fish: your pond size, the bio-filtration capacity, the species of fish, and your overwintering method.

Is my pond big enough for fish? How many?

Pond fish require about 10 to 13 US Gallons of water for every inch of pond fish. Remember that pond fish can grow rapidly over the course of a single season – from 3” to 6” or more in one summer! Take fish growth into consideration when planning how many fish your pond can ideally hold.

Factor in the maximum potential growth of your fish when choosing which species of fish you want to add to your pond. Koi fish can grow to a whopping 20-30”, while goldfish top out around 10”.

Just as in fish aquariums, pond fish do better when their numbers are well under the maximum capacity for your pond. Less fish in your pond often means healthier and more vibrant pond fish.

What is my pond bio-filtration capacity?


While it’s a mouthful, your pond’s bio-filtration capacity is a simple concept. Waterfalls, streams, and oversized bio filters increase the air exchange that your pond has. The more oxygen your pond produces, the more fish it can handle.

Bio filters, as well as natural waterfalls and streams, increase the surface area where beneficial bacteria have contact with your pond water. This boost to your pond’s natural nitrogen cycle decreases the amount of harmful toxins in the water. What’s left? An ideal environment for more fish!

What type of pond fish is best for my pond?


goldfishGoldfish are the top choice for smaller ponds as they reach a maximum size of 10 inches.

Comets or basic goldfish (pictured above) are hardy and inexpensive. The downside? They have limited colouration and variations.

Sarasa comets are physically identical to basic comets, but their colouration is a fancy orange and white. These cost slightly more than your basic comets, but are still an affordable option.

sarasa comet goldfish

(Sarasa Comet Goldfish)

Shubunkins are also physically identical to comets, but they are multi-coloured. Shubunkins have a mix of black, white, and orange.

shubunkin goldfish

(Shubunkin Goldfish)

Fancy goldfish varieties (Fantails, Lionheads, Moors, Orandas) make beautiful pond fish because of their unique physical traits. They may be more expensive than comet goldfish, but they are just as hardy. The exception to this rule may be the Black Moor fish. Black Moors have poor eyesight, which makes competing for food in a murky pond environment difficult.

black moor goldfish(Black Moor Goldfish)


koi pond fish

Koi are a traditional Japanese decorative pond fish that have been bred for thousands of years. There are hundreds of varieties of koi in a wide range of prices from a few dollars to thousands for very large and fancy types.

Koi are social fish and very hardy, which makes them ideal for large pond use. Since they grow to between 20 and 30 inches, they thrive in large ponds of 1000 Gallons or more. Need to winterize your fish in your pond? Unless your pond is very deep, it can be difficult to winter your aged koi outside as they get larger.


How do I choose healthy pond fish?

Avoid fish that:

  • Are inactive.
  • Have cloudy eyes.
  • Have irregular scales.
  • Have marks on their body.
  • Are gasping for air.
  • Are isolated from the group.
  • Are gasping for air at the surface.
  • Have clamped fins.
  • Have red on their gills or tail.

Choose fish that:

  • Are active.
  • Are swimming with the rest of the fish.
  • Are clear-eyed and healthy looking.
  • Have wide open fins.
  • Are interactive.