pump problem on pond

[coarb34]

hi all
ive got a 2000 litre pond which has 5 fantails and one koi. Running two pumps on it,one to circulate the pond and one for the filter.
the filter pump once cleaned works well for two or three hours then slows down, the funny part of it is it is rated for a pond three times the size. max height of the the pum to filter is 1.5 metres, the rated max of the pump is 5 metres, everything in the pump is cleaned, main filter and piping is clean.
any help would be welcome. the pump is one month old

[metal-otaku]

i'd be checking it the area you placed it for loose leaves or plants that are blocking it. i have mine sitting on a flat rock surface just above the base ground of my pound so it's not sucking up sand or the bottom substrate of the pond. if you have lilies or any other plants the dead leaves and stuff might be getting sucked into it and inhibiting the flow.

[coarb34]

thanks metal otaka

[Aeonflame]

Does the pump have a prefilter on it?

[mrgoodkat]

I wouldn't go for a prefilter in a pond, they clog too easy. Either get a plastic cage for the pump or one of those protection bags.
Like this: http://www.pondandgardenwholesalers.com/servlet/the-1693/Pondmaster-Pump-protection-bag/Detail

Are both pumps you are using rated for the same flow? If the pumps are rated for different flow, one of them will run at zero pressure, causing gas bubbles to be formed in the pump.
It's better to use a canister filter without a pump and push water through with only one pump.

[coarb34]

the one to the main filter is rated at 12000 litres per hour, ill belive its closer to a quarter of that. the second is rated at 300/hour and the second just rotates the water around the pond

[smaug]

One of those protection bags would help but unless you have a very well made pump then it will always have issues with the dirty water of a pond.

[Aeonflame]

I wouldn't go for a prefilter in a pond, they clog too easy. .

This is why I asked if he uses a prefilter. A mesh makeup bag can work as well

[coarb34]

both came with a sponge filter in, toke the one of circulating the pond. and put the main pump on a brick and seems to be working fine for the time bieng