Thread: Filtration help needed

Hi everyone,
first post so be gentle please!
Im just after a little advice regarding the pond I’ve kind of taken over from my dad.
it’s a 5000l pond with half a dozen small koi (sub 5”) that are around 6 months old and about 15 small goldfish (that they’ve had since the beginning of time).
he originally had an oasis pressure filter and a pump turning over about 2k litres an hour, in fairness he cleaned it regularly but the water quality wasn’t great visibility wise although the water tests came back pretty well. Since ive involved myself I looked into many options of redoing the filter system but unfortunately without a major upheaval we are stuck in a pressure filter situation due to the way the pond was built and the returns coming in at the top and not being able to put any kind of gravity system as it doesn’t work with the geography of the garden. So I added another pressure filter and pump system separate from the original but overspecced it so I added a large pump and the largest fiktoclear oase 31000. He pond is turning over around its capacity in one hour with plenty left in the pump should I need to increase the flow rate.Since doing this the water quality has gone almost crystal, all the blanket weed has disappeared and the fish are feeding a lot more readily. However the water tests are not coming back as good as they were before. Ph 7.5, nitrite between 0.25-0.5, carbonate hardness 6, ammonia somewhere around 0.25, nitrate between 5 and 10 on the pond lab test (not sure how to interpret the numbers!).
im unsure what to do, both filters were cleaned back to scratch around a month ago when the larger filter was added and I understand that by doing this I’ve killed of any bio filtration that may have been in the pressure canisters. I know they’re not great but I’m stuck with that setup.
could it be worth me putting a tempest inline after the pressure filter to add bio filtration? Or is it a case of waiting to see if that naturally occurs. I’ve also read about something you can add to the filter that starts off a bio colony but I’m unsure if they work inside a pressure hellhole.
any help would be great and much appreciated

Originally Posted by Archstanton

Hi everyone,
first post so be gentle please!
Im just after a little advice regarding the pond I’ve kind of taken over from my dad.
it’s a 5000l pond with half a dozen small koi (sub 5”) that are around 6 months old and about 15 small goldfish (that they’ve had since the beginning of time).
he originally had an oasis pressure filter and a pump turning over about 2k litres an hour, in fairness he cleaned it regularly but the water quality wasn’t great visibility wise although the water tests came back pretty well. Since ive involved myself I looked into many options of redoing the filter system but unfortunately without a major upheaval we are stuck in a pressure filter situation due to the way the pond was built and the returns coming in at the top and not being able to put any kind of gravity system as it doesn’t work with the geography of the garden. So I added another pressure filter and pump system separate from the original but overspecced it so I added a large pump and the largest fiktoclear oase 31000. He pond is turning over around its capacity in one hour with plenty left in the pump should I need to increase the flow rate.Since doing this the water quality has gone almost crystal, all the blanket weed has disappeared and the fish are feeding a lot more readily. However the water tests are not coming back as good as they were before. Ph 7.5, nitrite between 0.25-0.5, carbonate hardness 6, ammonia somewhere around 0.25, nitrate between 5 and 10 on the pond lab test (not sure how to interpret the numbers!).
im unsure what to do, both filters were cleaned back to scratch around a month ago when the larger filter was added and I understand that by doing this I’ve killed of any bio filtration that may have been in the pressure canisters. I know they’re not great but I’m stuck with that setup.
could it be worth me putting a tempest inline after the pressure filter to add bio filtration? Or is it a case of waiting to see if that naturally occurs. I’ve also read about something you can add to the filter that starts off a bio colony but I’m unsure if they work inside a pressure hellhole.
any help would be great and much appreciated

Hi. Welcome to the forum. With speeding up the flow rate it sounds like you are filtering more waste etc out. But the filters aren't having enough gel time for the biological to strip out the Ammonia and nitrite. Pressure filters aren't really good all round filters. They are made for much smaller ponds then they are spec for. Have you got the money and room for a nexus 220 or easy pod? Another reason could be because you are turning more water over, the fish are more hungry. And you are feeding more and the filters just can't cope now. The Tempest is only really for fines, very little bio capacity. As the koi grow and they will, you will need to upgrade the filters or move some fish on. For short term fixes you can use a product called Envirex which lower Ammonia and Nitrite etc. Hope that helps, there's a lot to think about.

Thanks for both replies, unfortunately there’s just no way I can accommodate anything that involves gravity returns or intakes and whole system has to function on a pump loop so to speak. The pond is raised above ground with 2” pipe and the return enters at the top of the pond. I’m hoping that given time the bio can reform within the pond, I don’t have much hope for the bio inside the filter as I know those filters don’t provide a great environment so it was just a case of seeing if I could put anything inline after the pressure filter really as it feels like my only option.

I’ll take some and put them on later in the week, I’m working away for a couple of days. That would be great if you have any once you’ve seen it. The only other thing I could think of is where the 2” returns the water at the top of the pond I could set up a t bar kind of situation with a few holes knocked and build a kind of long tray that spans the width of the pond to make a kind of shower that I could fill with media, I’m guessing it would minimise flow though and oxygen. I could possibly draw a sketch on the computer.