leave it at that for now, if you have no fish left in the other tiny tank take that filter and put it on the big tank. then take alittl bit of the gunk youll find and put that in the new filter. wait 2 weeks (be sure to be testing the water throughout and make water changes accordingly) and when all is good then get i think maybe another angel, a school of cories, another school of fish like gold barbs or some other tetra (make sure they are not fin nippers) and maybe another angel.
if you still have fish in te small tank then just do the gunk thing, but yull end up waiting longer and performing more water changes (wc)
