I have 17 salamandra salamandra larva that were laid in my tank same as yours. I noticed the female in the water bowl (about 1" of water) and as soon as she left on her own I replaced it with a much larger bowl. The water is still shallow as adult fire salamanders can drown so, easy in, easy out. She laid 4 larva at first, then two days later 5 more, 2 weeks later 6 more and half a week after that the last 2. Every morning I would check the bowl and remove the larva if they were there. I raised them in tupper in the groups that they were born with. The tupper is around 6x9 inch's and the water about 1 or 2 inch's deep. I change 100% around twice a week. My larva was nice to each other and I had very few gills get eaten. They love live blackworms. I would suggest moving the trouble maker to it's own tupper and if your worried, seperate them all. It just means more work for you but you might like the peace of mind. They stayed in the water for around 6 weeks. I keep a nice chunk of elodea plant in with them to help them get to the surface. When they start to lose there gills it happens fast, say 2 days. I then put them in a sealed tupper of moss and water, mostly moss, that brick stuff you can buy . The idea is to keep humidity high and make it so they cant drown. Other salamander larva I might keep in this tupper for a week but the fire's are active and ready to come out in about 2 days. I then transfer them to anouther sealed tupper with dirt and plants and rocks. I dont normally offer food for about a week because they are still morphing and it will probably just stress them. They now actively hunt for pinheads and I have had no deaths. All but two have morphed and color is evident around a week after they went into the planted set-up. The other thing is there cute as hell. I hope this helps