fish not eating

So I have a few "problem fish" who aren't eating any thing. My 6 or so
inch delhezi and my 4 3 inch balzanis. The balzanis are in a 30 gallon with
lots of hiding spots and alot of filtration, nitrates and amonia are 0, temp
is around 76, and I believe ph is around 7. The delhezi is in a 55 with my
male fh (5 inches), 2 4 inch male festae that are soon gonna be outa
there, and a 6 inch blind rtc. Tank is also at 76 degrees, nitrates are very
low, and I believe ph is around 6.8.

is the del being intimidated by those fish? Are you offering sinking pellets? They eat based on smell, so if the other fish are getting there first they are out of luck. They are easy to train to feed from tongs, and usually earthworms/red worms, etc will get them to eat readily.

Assuming the balzani are the ones you got this weekend from Dan, I'd give them some time before getting worried. They may still be stressed out from the trip.

You've got some pretty aggressive fish in a relatively small tank, so I would agree with Rachel that the bicher is probably being out competed for food.

We use a piece of 1/2" PVC pipe (available in 3-foot lengths for about $1 at Home Depot) to direct food to our catfish, at least we did back when Piranhas also inhabited that tank... these days they have no real competition. You just put the tube in the water, point it at where you want the food to go, drop in sinking pellets, and shake it lightly to make sure they all sink.

The bichir is not being out competed too much, the flower horn tres to gobble up as much as he can but about half of them sink and it takes a little bit for the other fish to realize that.

And yes, the balzani are from coa.

Can you separate the flowerhorn temporarily with a divider when you remove the festae? If he gets food when he is basically in his own tank, then it is likely the tankmate(s) directly or indirectly causing the problem.

You also can try target feeding as mentioned earlier.