I don't know what they use in shops, but a mild bleach solution would work. You'd want to rinse the net before using it, of course. Straight bleach would probably eat your net too quickly.
Isopropyl alchohol kills most things (including fish) and evaporates quickly leaving no residue.
Potassium permanganate will get a lot of things too, but I'm not sure if it would work for a quick dip, and I'm not sure if it would kill KHV.
The fish store clerks might just be using fresh water for the saltwater tanks, and salt water for the freshwater tanks. This won't actually sterilize the nets, but if they left the nets in for a while, it would kill quite a few parasites.
If you ask at the fish store, tell us what they say.
Orfe are said to be more sensitive to salt than koi or goldfish, but I'm not sure what their limits are.
I'm certainly not going to dose it to anywhere near the concentration of sea water and I'm not entirely convinced that salt is bad for freshwater fish.
I understand that you're not going to try to turn your pond into the ocean, but why raise salt above the level for which the fish evolved? I know many people add low levels of salt as a matter of course, and it doesn't seem to be doing too much harm. But does it really do that much good in the long run?
I think the reason for the conflicting opinions on this one is that the effects are subtle and the subject has never been adequately studied. Whatever theory you believe, it's easy to interpret what you see as confirmation. I claim no certain knowledge. But if it isn't broken, I'd rather not try to fix it.
You need to forget the word salt and think in terms of osmotic potential.
I've forgotten enough already. But whether it's salinity or osmotic potential, I think the ideal is still as close as you can get to the environment the fish would have in the wild. There should be no osmotic stress for a healthy fish in the sort of water for which it was born.
Now, I agree that if a heron puts a big hole in one of your fish, some salt might help the fish maintain equilibrium until it heals. But one trouble with using medications all the time is that the fish and their pathogens will adapt to the drug, and then the it won't be as effective. I honestly don't know how big a factor is that with salt, but some of the "experts" believe that it's better to wait until you actually need salt, and that makes sense to me.
It depends. What sort of fish do you have in your pond? Any amphibians? Snails?
Also, why are you adding salt? It's useful as a medication, but the main reason people add salt is that it will cause fish to secrete a thicker slime coat. And the reason they will secrete more slime is that they are freshwater fish, and need to protect themselves from the salt. Many disagree with me, of course, but it seems to me that most of the fish we keep evolved for millions of years in water without much salt, and hence, they're really better off without it.
Another thought. If you have a cycled tank you could keep your goldfish in for a few weeks. You could take them out of the pond and continue to cycle it by adding ammonia (if you can find a bottle without additives) and/or fishfood. When the pond can handle this, put the fish back in. This would probably be less stress for both you and the fish than cycling the system with them in it.
The nitrite reading of 0.3ppm indicates that your nitrifying bacteria are not up to speed yet. It is also high enough to stress your fish, though I doubt it will kill them outright. You could lower it by changing half the water. Adding salt is said to protect fish from nitrite by thickening their slime coat. However, the reason they secrete more slime is that they are freshwater fish and need to protect themselves from the salt. Why their slime doesn't thicken in response to nitrite, I don't know. Perhaps it does, and the salt just makes fish keepers feel better. The other downside to adding salt is that it will slow the growth of your bacteria colonies. I'd probably do the water change and not bother with salt, but I'm fairly new to keeping fish in ponds too, so don't take this as expert advice. Either way, you should monitor nitrite daily until it's gone. Try to keep it under 0.25 ppm. Feed very lightly until you get the nitrite under control. And watch for a buildup of nitrate as the nitrite levels become undetectable. If you're using strips, you should probably get a liquid test kit. The strips are notoriously inaccurate. All of this may be familiar from keeping aquariums.
The murk is probably just suspended algae. How deep is your pond? As you've seen, what makes a pond murky near the bottom looks crystal clear in a smaller container. Hence you'll notice algae levels in your pond that would be undetectable in your tanks. It may clear up when your bacteria get going. Barley extract would be a good quick fix for the green water. The algae won't hurt your fish, though, so concentrate on the nitrite first. In fact, algae will do some of the work the bacteria should be doing.
Another possibility is that the murk is fine soil particles that got washed into the pond during a rainstorm. If this can happen, you should correct the problem soon, as it will become a major headache if left unchecked.
Food has been eaten over night too, all gone when we checked this am.
Any ideas on what's going on?
You may be overfeeding. Generally, it's a bad idea to feed more than the fish will eat in five minutes. Of course, if the fish won't come out to eat while you're there, this rule of thumb is difficult to apply. But it's hard to starve a fish to death in a pond, and if they get hungry enough they'll come out.
If you have a tall, clear vase, fill it with pond water and look down through it at a white background, so that you are looking as far through the water as possible. This might give you a better sense of what color the water is.
And if I understood the above explanation correctly, you're not actually pumping the water very high at all. It's the difference in the waterlines that matters. The four feet of water above the pump offsets the weight of the four feet of water between the outlet and the waterline. Hence you have very little static head, and unless your filter or tubing is highly restrictive, you may be running the water past the UV so fast that most of the algae cells survive to reproduce. Rigging a bypass so that some of the water goes around the UV would fix this. Be careful not to decrease the flow through the clarifier too much, though. If you can use a stronger bulb or add another UV source, that would be even better.
How many gallons in your pond, what is the flow rate through your UV clarifier, and how many watts is it? I know you checked the bulb, but if the system is working (as opposed to just being on), you really shouldn't have such green water.
Are these filters placed partly below grade? If so, it may be that the soil is shifting and putting more pressure on them than they can handle. It's simple to prevent this. You just need the right gravel around them.