In my opinion you are too overstocked in your 55. I have been breeding JD's for a little while, and currently have a batch of fry that have been free swimming for 3 days. My pair is in a 75, by themselves, and when my female doesn't want to breed EVERY month or two like the male does, she still has to swim across the whole 75, and hide in and out of the clay flowerpots, and caves that are in the aquarium. I have never personally tried it, but from the advice that I've read and been given, breeding JD's in a 55 can work fine, but they should be the only one's, except possible dithers, in there. The babies could have disappeared for several reasons. Sometimes it takes the parents a little while to get things right. My pair did not raise any fry the first couple of times. Both parents, once they get it right, will protect and raise the fry, and there is no reason to separate either parent from the fry until they get bigger. Once the parents start showing a lose of interest in the fry, or appear to be getting ready to breed again than you will need to separate the fry. Also, if the parents get too stressed from protecting the fry they will eat their own fry. Make sure all of the intakes on your filters are covered so there are not big hole in it in which your fry can be sucked up into. You might want to check your filter to see if there are any in there. Also, if you want to raise fry make sure you don't get a pleco, as they have a good and just reputation for eating the eggs at night. I raise my fry in a 30 gallon until they get big enough for one of a couple of LFS's that will take them. If neither store needs the fry, I, though it sounds cruel, use them as feeders.