engineer gobies produce hundreds of extremely large fry (that hatch w/ a large yolks sac). The fry are so large they can be fed baby brine shrimp as first food. While spawning is infrequent in the home aquarium, there have been a number of reports suggesting it does happen
If you want to have any success w/ these fry you'll have to remove them from the display tank
The good news for you is that very few (if any) commercial firms are producing this fish, so if you can isolate the breeding pair, you can corner the market