I personally wouldn't recommend temperatures above 80s for ebjd unless you are treating them for ich/parasites w/ addition of salt. Ebjd are prone to SBD and bloat and their scales are very sensitive so they stress easily.
Im keeping 8 in a 60gal at the moment since they were 1", w/temp between 74-76f, and feed ONLY flakes when they are juvies as again, they can get SBD/bloat if fed pellets they cant digest when they are young.
Ive seen about 100 juvie ebjd living off of no heater for weeks, as long as you keep up the water changes and feed them flake food that also has garlic(such as NLS) to prevent any parasites.
Also to the OP, my recommendation would be to keep the ebjd solitary or w/ other Ebjd's in a 20gal min. for 1ebjd if you really want to see their true amazing colors come out as once they get too stressed, they darken up.
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I think that it's a matter of preference. I know a guy who keeps all of his EBJD at 80-83 degrees F, and feeds mainly live/frozen food to them. All of his have made it to 5 inches, and are still currently alive.
I've been taking his word and keeping my tank at 79-82degrees F, because I have others in the tank that prefer their temps not above 82. And so far mine has been really healthy, and keeping his colors really bright. Also has grown a bit since I've had him, for maybe a month and a half.