Good to know. Also for a cave would a artificial cave be better or natural rock like mine currently has spawned under?If they weren't viable or fertilised, I would have expected the eggs to be white or fungused by now; don't forget hatching times can vary slightly, according to water hardness, temperature and some other factors, like the age of the parents.
For a breeding tank, you want something around 20 gallons, preferably with a sponge filter and lots of plants and wood; you want it to be a bit scruffy and overgrown. Not all fish need dithers; try them without first.