My goldfish in my outdoor pond (4900 litres) have started to get a white film on their bodies and the smallers ones are on top of pond not doing well at all. i have tested water and it's PH is high. I have a large filter system and the water is very clear. There is a mixture of koi and goldfish in the pond. Some of the big fantails have a bit of fraying on their fins as well. Can anybody offer any help.
thank you.

I did check for nitrates and that test was clear, i live in temperate climate so not very cold here. i have about 50 fish all sizes in pond and a lot of water lilies as well but of course they are not growing at moment as we are coming off winter. i am going to petshop today to get an antibiotic and dose the pond. i don't know know exact ph as I just tested it against the card that was in the kit and it was in the blue. i am just an amatuer at this, have had the pond 3 years and have not had a problem before. we have had a lot of rain recently and i have not done a water change recently. should i do one now? I also noticed 1 of the bigger fish has a lump on it. The fish range from 1" up to 7" long not very big.
how big should the air pump be? Does adding zeolite to pond help?
appreciate your help thankyou

I think the ph reading was above 9, i have since been to shops and bought a broad spectrum trament for the fish and some ph downer and have treated the pond as per instructions.
 i will test again today and see if any better.
 I live in Western Australia, in the north of the state. quite mild temperatures but we have had heaps of rain recently.  That is the only difference over the season.
I also tested again for nitrates and there are none showing up.

pH above nine would annihilate any aquatic life, so that's probably out of question... I think your pond is suffering from new tank (or "pond" in this case?) syndrome, and it may also be a bit crowded.

Here's what you should do:
- Test everything, and give exact results! pH, ammonia, nitrite and nitrate
- Buy a good water conditioner/bio filter booster. I've got Easy Life Fluid Filter Medium, which is pretty much a water conditioner and a bio filter booster in one so you won't need two bottles. Very good stuff! It will not only help the beneficial bacteria in the pond but also take care of smaller wounds and infections of the fish as well as strengthen their immune system. (It will also neutralize ammonia and chemicals)
- Do a major water change if anything's wrong, at least 50% and dose for the whole pond.
- See if you can get rid of the koi (as in: give away), because they will grow huge. They need lots of space, and might bully the goldfish.
- After this is done, add some anti-bacterial medication, no melafix, pimafix or any cr*p like that. It won't deal with any bacteria. But something for bacterial infections, something specifically for fin rot would be ideal!
- Now you should be testing the water daily, pH and everything else. Change a bit of water whenever the ammonia, nitrite or nitrates are too high. Always replace the dosage of medication, as well as the dose of water conditioner and bio filter booster.
- Observe your fish, and wait.

Good luck