Having trouble with your Ruby Red Dragonets? I feel you. Right now I am trying to go about mating my two mandarinfish together. I'd say they'd feel way more comfortable with coral, ulva sea lettuce, and plenty of sand and live rock. Remember to provide regular nighttime lighting and ample food and shelter. GO to Dr. Foster and Smith and you'll find some jar w/a picture of a blue mandarinfish on it labeled "Rubble Rock," that really helped my finger dragonets to get to their first spawn.
Best Wishes,
FlameAngelfish
P.S.
If the tank isn't tall enough or they have aggressive or egg-eating tankmates the ruby reds won't spawn anyways. Plus mandarinfish have a spawning season that's fixed with all other reef inhabitants. Trick them into thinking that the season's here by getting some of Dr. Eco System's "Doc's Eco Eggs" to try and fool them. Either it works or the dragonets eat up the eggs like crazy. When all else fails, tell me and I'll do what I can for you w/last resorts in the breeding process.