Choose Pond Pumps for Fish Ponds or Plants Only Ponds

If your pond will contain fish you need to consider different factors for a pump than if you do not intend to stock fish in your garden pond. Both the initial and running costs will be considerably less for an pond with no fish than for one that is stocked with goldfish and if you stock  the fishpond with koi then the pump will probably be bigger and more expensive than the one for goldfish. Why?

Let's deal with the plants-only pond first.

Because there are no fish present the pond will not be polluted by fish faeces, urine and other bodily functions and as such the rate at which pond water will become less pure will be far lower and you may be able to maintain pristine conditions by using enough of the right aquatic plants  .

Even though you do not stock fish you may still want a waterfall or stream cascading into the pond to add character and of course this will need a pump to be specified based upon waterfall characteristics.

If you don't want a waterfall then a pump is a good idea just to prevent stagnant areas developing. For such a situation a pond pump that will create a flow rate of about half the ponds volume every 3 to 4 hour is the specification required. It's that simple. So to be specific if you have a planted pond of 10,000 litres or thereabouts a pump that will deliver approximately 3,000 litres per hour will be ideal. If the flow is only 2,000 it won't make much difference.

Pumps for Ponds with Goldfish

Ponds that contain goldfish create less pollution than koi ponds. The reason is that goldfish grow far more slowly and eat far less than koi ... and it the normal metabolic process associated with breathing and eating that cause most of the problems people experience in ponds.

If your fish for whatever reason eat 100gm of food a day then the amount of pollution that will occur in your pond will be double than if you fed only 50 gms of fish food per day. Because the pollution is lower then the bacteria in the pond filter need to work less hard and all equipment associated with pond filtration including the pump can also be slowed down (read made less expensive).

The rule of thumb for specifying the pump flow rate is half the pond's volume per hour. If your pond is 10,000 litres then a good flow rate would be about 5,000 litres per hour at a pump head of about 50 cm (to allow for pressure losses).

Pumps for Ponds with Larger Koi

Koi keepers generally prefer to pump higher volumes of water through their filtration equipment. Many also prefer to create currents within the actual pond against which koi can swim and thereby improve their shape (refer Nishikoi International koi magazine). In general pump the pond volume around the system at least every hour. As an example if your pond is 10,000 litres then use a pump that can generate that flow of 10,000 litres per hour at say 75 cm head (assumes no waterfall). Most koi ponds have waterfalls so to correctly specify the pump you need to follow the "rules" for waterfall pump specification.

Pond Keeping Units

Now we've started to talk litres you might find this table below useful. It helps to translate one set of units to another quite easily.

Example ... 1 cu.m per minute is the same as 1,000 litres per minute or 35.32 cu.ft per min or 220 imperial gallons per minute.

I have created 12 different pond calculators and these are available free at my other site Perfect Pond Keeping . These calculators allow you to calculate almost anything to do with a pond. One allows you to calculate easily the volume of any shaped pond. You might find this calculator useful in view of the above discussion. Another allows you to accurately specify any pond pump for any situation even taking pipe friction losses into account. I would suggest you get these Excel calculators and play around with them. They'll definitely save you money.

Factors to be aware of with all pumps. This is a good page to read before you buy any pump.