Combining 2 fish tanks

[Zappa]

I have a 44 gallon tank with 5 neon tetras, 2 regosa, 2 hatchets, a silver dollar, a black skirt tetra and a julie catfish. I also have a 16 gallon tank with 3 upside down catfish which have grown quite large over the past 4 years and 1 yellow gourami. I’m going to put the fish in the 16 gallon into the 44 gallon. Any advise here? I’m a little worried

 

[Autumnsky]

About making a change, adding too many fish for the bioload at once, or if the Upside down cats might snack on the Neons, or ???

I would be a bit hesitant with the possible snacking at night on little fish, and they might be fine for a while and then one time it accidentally scoops one up, tastes good, and then it likes to eat them. I once had a large Angelfish, after living with them for a year (of course the fish got bigger...) but then in a week ate half (there were 50-60) of them before I caught him with one in his mouth, tail sticking out!