Your fish won't starve since there is plenty of natural food in the pond. Just throw in a little bit and remove it after a while if they don't eat it. They will soon get the hang of eating on the surface.

I only have one baby koi and the rest are goldfish, but so far I've seen both the koi and goldies slurp them up, but it doesn't take long for them to shoot them back out. One poor tad was cannoned halfway across the pond and landed on a rock, but it was okay and wiggled back into the water. It may be that they are spoilt. I still have hundreds and hundreds of toadpoles in there and they are growing quickly. This years "crop" are much larger, faster than last year, which surprises me a little as we have had cooler temps than usual, although now it is starting to warm up.

I have a indoor 125 gallon pond with two Koi. Both very healthy. Water changed three times a week. They will be Bonzai Koi.They live with a lion head goldfish, 4 Gouramis, 1 Bala Shark, 2 long skirted small tetras . All get along fine all are healthy. Now back to what I wanted to say. I have a long skirted Tetra that did not eat for a month. Have a few plants in the pond so I thought maybe she was eating some of those. Never saw her though. She is on the skinny side. Did not seem to be sick, not hiding, swimming with the others. I only use salt if my fish get sick. I have never had success with antibiotics ( do not reach for over the counter meds at all) (If it is the fishes time to pass on I let them) (For me this has been rare once fish established). All the fish died when I use to reach for antibiotics. Now I keep clean water and do water tests. I do keep a jungle food antibiotic on hand for those still eating ( fish has to eat pellet, so if not eating then it is up to fate). Right now I never keep salt in the water. Only use it when sickness is found, and only in a small 10 gallon pond that works as a quarantine exception would be if ich was found in the main pond or more than one fish sick. Amount I use when sickness is in pond is 2% to 3% salt which is 2 tablespoons per 5 gallons or 3 tablespoons per 5 gallons. Today after one month the Tetra came up and ate some blood worms. Often the fish's immune systems heal them. I rarely have sickness. All my fish fed frozen foods, greens, and oranges , etc.... Fish have a real slow metabolism and can go a long time without food. If your fish is not hiding out, swimming with the others, acting normal, then why fill it with a lot of chemicals. Let nature do its thing. I usually just keep my eye on it.

I'm fairly new to ponding but I just stumbled on your post here. You should try posting it over on the "ponds" forum. It seems like people (with alot of experience) frequent that board alot more than here. Hope your fish are doing better :)