Can you use some of the filter media from your established tank and get it in the new one ? just some of it ?
Gravel doesnt contain that much bacteria really.
You also need a small fry type filter otherwise they get sucked up, they usually cost about £3 and run off an air pump.
Other than that they probably will get eaten, im suprised if they havent already. You could also use a breeding net until you get sorted out, although they are NOT ideal for more than a few days.
They need feeding about 3-5 times a day, a small ammount, but very small food, either tetra fry food or liquifry 1 for the time being.