Fish Pond Pumps

Fish pond pumps are the heart and lifeblood of many fish ponds and it is important to have some sense of what you're getting into and what your expectations are before you purchase a pump.

Rules Of Thumb

There are several rules of thumb for keeping fish in a pond - they disagree somewhat but the low end is the trouble free zone and the high end starts to put you at risk.

Go above these figures with your garden ponds and you're looking for trouble.

One Inch Of Fish

One inch of fish for every square foot of water. So a 10-inch fish requires 10 square feet of water in a normal pond.

This doesn't take into account water depth.

Number Of Fish Per Gallon

One 6" fish for every hundred gallons of water. This takes into account water depth and surface.

1" of fish per 10 gallons of water This is closer to the high end estimate based on your fish pond pumps working.

Gallons Divided By 200

Total gallons of pond divided by 200 = Total 6" fish in pond (if the pond has 400 gallons, then you can have 2 x 6-inch fish or 1 x 12-inch fish or 3 x 4-inch fish.) This is the low-end.

Fish farmers use a pounds per cubic foot of water (called fish-density) and an intensively managed trout pond can go to 4.5 pounds of fish per cubic foot of water (on average). If you can weigh your fish and aerate to the maximum, you can maintain this high commercial level of fish as well. This is high-density fish raising with maximum water volumes being moved and no plants or other environmental features.


Unfortunately, there is no hard and fast rule that says "increase the fish pond pumps size by X and you can keep Y fish". The amount of fish you can keep (called the "carrying capacity") depends not only on the volume of water you're circulating but is also influenced by water temperature, pond volume and pond water chemistry.

The Danger

The danger in increasing the number and/size of fish beyond the natural carrying capacity of the pond is that in case of pump or power failure, you're going to lose fish.

By running fish pond pumps, you'll be making sure the water quality is high as you'll be pumping water through various particle filters and bio-filters to removes solids and fish wastes.

If you want my .02 (hey, that's why you're here) then I'd figure out how many inches of fish I wanted - then I'd build a bigger natural pond (with waterfall) to house them. This is the no-fuss method of pond maintenance as the pond and the fish interact naturally.

You can see some fish pond pump options here

Right Website

If you only want fish - no plants - no waterfalls etc. Then you're probably in the wrong website. (no hard feelings, I write for home gardeners and those interested in water gardening - not fish raising)

See this section on pond pumps to get everything you need to know about the actual pumps themselves.