Is the EBJD the only fish in the tank right now? If it is I would leave it alone and not do anythig that would stress it. It seems at between 3 and 4" EBJD's pass that critacal stage in development and get a little tougher. When you're ready to introduce a new fish make sure to quarintine it and treat for intsetinal parasites. Then a smaller JD would be fine, two JDs in a 55 makes a nice display. Also EBJDs are generally less agressive than regular JDs and IMO a Tex would be too much for it + the tank really is'nt big enough.