For ponds of up to 40,000 litres, our pond was about 10,000 litres with large Koi so this was a belt and braces unit for us. Lotus Clear Pond 50 including hoses and fitting. This system is possibly the best filter we have ever used and kept our pond water crystal clear even in full sun.
eBay
Air Purifiers for Bedroom Kitchen Quiet Air Cleaner with H11 HEPA Filter Portable with 2 Speeds for Allergies Pollen Pet Dust
Aliexpress UK
bought 3 yrs Ago for our ponds we have now upgraded to a new electric filter so this is no longer needed I will add the size of the filter later today. collection only and within 7 days please
eBay
Pet Hair Remover Reusable Ball Laundry Washing Machine Filter Wool Sticker Cat Hair Remover Pet Fur Lint Catcher pet grooming
Aliexpress UK
The Aquadrum 25 Combi Deluxe is an all-in-one pond filtration system that utilizes ultraviolet light and drum filtration methods. Made by the brand Aquadrum, this product offers a convenient solution for maintaining clean and clear water in your garden or patio pond. Its sleek design and efficient filtration capabilities make it a popular choice for those looking to enhance the beauty of their outdoor water features. Built in rinse pump. Plug and play Self cleaning drum Uv built in Media bed compartment L Return pump included Air pump included Media included. Recent new motor/gearbox (£400) 3 4inch valves included 1 aerated bottom drain included. Delivery can be arranged. Ask before purchase.
eBay
10 PCS 5mm Humidifier Filter Cotton Swab Core USB Air Ultrasonic Humidifier Aroma Diffuser Replacement Cotton Sponge Stick
Aliexpress UK
I had this specially made for my old pond. This is approximately 5 foot high by 3 foot in a circle it filters, the Pond  then comes over the top as a waterfall. There is a drain valve for cleaning I also have a UV that will power. This will need a new bulb though will be extra. Buyer will need to collect. 
eBay
Air Purifiers for Bedroom Kitchen Quiet Air Cleaner with H11 HEPA Filter Portable with 2 Speeds for Allergies Pollen Pet Dust
Aliexpress UK
large bead filter, large vortex and 2 sequence pumps collection only.
eBay
High pressure water-saving spray 360 degree rotating turbine fan shower head adjustable shower head filter bathroom accessories
Aliexpress UK
koi pond sand filter.bought this in lock down to turn into protein skimmer but has never happened.never used it or know how it works.collection only from chipping Norton oxon.
eBay
360 degree rotating turbine fan shower head bathroom accessories high-pressure water-saving spray adjustable shower head filter
Aliexpress UK
KOI POND MULTI CHAMBER FIBREGLASS FILTER WITH VORTEX (GRAVITY FED). Its multi chamber design ensures maximum filtration with the minimum of maintenance. Each unit is suitable for fish ponds of 18,000 litres and a max flow rate of 11,000 litres per hour.
eBay
Sediment Water Filter Cartridge Replacement Filtration Water System Maximum 30 lpm
Aliexpress UK
Here for sale is my pressure filter 12000, I’ve decided to get a nexus so no longer needed Any question pls ask Cash on collection pls Collection March Cambridgeshire
eBay
Micro Landscape Fish Tank Home Silent Water Flow Aquarium Desktop Ornament Creative Imitation Stone Landscaping Fish Tank Filter
Aliexpress UK