Tannins, possibly?
Fish waste, other organic debris such as wind blown pollen and leaf litter (small pieces), insect poop, decomposing insects, dead algae, dead zooplankton, uneaten fish food, etc.. There is a myriad of things floating around in pond water, more in some ponds than others. Collectively it is called TSS (Total Suspended Solids).
It can b bacteria too i read about that rusty coloured thing somewhereExcellent reply, if i may say so. Pretty somes it up, can't think anything else myself. Just surprised how much in one day.
on the other hand debri and waste is more greyish blackish
When using carbon pads you shouldn't run them top, use a pre-filter pad and the carbon pad won't clog as quickly, learned that from experience. Also like Usman said you don't want to sterilize the pads, just remove most of the solids.
......and, carbon has to be replaced once it maxes out its capacity to filter.
Depending on the pond, carbon can become saturated within a few days.Which isn't very long, it is recommended to change carbon out every 4 weeks.
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.