Hi, is the tank he is in cycled and are you monitoring the water chemistry eg ammonia, ph? Are you being gentle with the water changes.
I've had fish jump out (down 6 ft) and just back into the same tank. Keep the water clean with water changes and should be fine. Normally I change 30% each week but might do a mid-week one here. A 100% water change is a lot for the fish to adjust to.
sounds too small (tbh, I'm wondering on the 100gal as well). I'd keep tank at 100%, small / regular water changes, check water chem readings and you could try something like API stress coat (but clean water is key). Also I wouldn't have water flow too strong for him and would have the tank where there isn't a lot of noise.
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