My 400 koi kohaku fry which are about 1/2" long have been doing just fine since I put them in the cage in my lake but the temps are going up (84 degrees water). I put the cage in the shade and I switched them from the 1.75' deep cage to my 2.5' deep cage when I seen some fry doing circles and sometimes floating upside down (i put the floaters in my small aquarium and 48 hours later their still swimming upside down). All my other 2"-10" koi in larger cages are doing good but I know fry are more delicate. I also have air stones in all the cages. I have a 75 gallon aquarium I could put them in until fall but the seller recommenced putting them in the pond? I have been feeding them 3 times a day with Aquatic Foods Baby & Fry Food but I have also put in soggy pellets that are dissolved.

How hot can the fry take? Is this a swim bladder issue that they already had, I'm causing or do some just develop this issue and die?

What should I do? Leave them in the lake cage with air stone or put them in 75 gallon tank inside home?

I also added a fountain about 2 months ago to the 3/4 acre pond which I run during the day and it seems the top and bottom water temp is the same at 84 degrees. Should I run the pump during the night when the air temps are near 75 degrees or leave it off so the bottom gets cooler? The fish cages are in about 4'-6' of water and at the deepest the pond is 8'.