In almost all species young can be reared initially in surprisingly large groups. Even a degree of crowding does not appear to cause any stress. In many case this can be seen in the wild, where initially animals hatched or metamorphosed at the same time and place will form little groups for a while.
Having said this, it is imperative to keep a very close eye on them and have further vivaria available as separate accommodation becomes necessary. Two particular signs to watch for are animals which are losing out to their larger brethren in the food stakes and are simply not growing as fast, and, especially with lizards, watch carefully for signs of aggression and separate the animals before tails and feet go missing!
I must admit that with the few amphibians I keep I do very little in the way of specific rearing. The vast majority are in natural or near natural environments and are left to fend for themselves. Since those natural environments (outdoor reptiliaries and greenhouses) are free of predators (apart from other amphibians) there is a naturally a much higher survival rate than might otherwise be the case.
Nonetheless, some tadpoles are removed immediately prior to metamorphosis for rearing. In all the species I keep, techniques are much the same. A mixed land/water (50/50) vivarium is prepared and provided with low-level UV emitting tubes together with a heat source where necessary. The tadpoles are not feeding at this time their main sustenance coming from absorbing their tails. With the mixed environment they emerge from the water quite naturally and find hiding places on the ground or, in the tree-frogs take to the natural plant growth I have in these vivaria (most commonly Scindapsus (Devil's Ivy) which thrives in warmth and high humidity).
At this stage most newly metamorphosed anurans are extremely small and their initial diet consists of hatchling crickets which have been dusted with vitamin powder. As they grow, the food size is increased. By the time they reach about 25mm they will take mini-mealworms and, according to the species the food size will continue to increase with their growth.
Growth is extremely rapid and most can be put back with the adults within about 3 months.
Lizards are able to fend for themselves right from hatching or birth. They may not feed for the first day or two but soon after any remaining yolk sac is absorbed healthy young tend to become stomachs on legs! Unlike adult lizards it is almost impossible to overfeed them since, if being kept properly, their food is converted primarily into growth rather than fat storage. This also stresses the need for a protein heavy diet at this stage in their lives rather than carbohydrate biased. This is extremely notable in species which are herbivorous or omnivorous as adults. In many such species the young are predominantly insectivorous.
Accordingly they are kept in much the same environment as the adults albeit on a somewhat smaller scale. UV lighting is essential - in fact all the vivarium requirements already discussed should be emulated. Food, consisting of vitamin dusted and gut loaded invertebrates of appropriate size are offered. Basically, as much as they will eat. The definition of "appropriate size" is, of course, immensely variable. In Lacertids a newly born Viviparous Lizard or Wall Lizard will need hatchling or second instar crickets. Sand Lizards can manage slightly larger and small grubs such as buffalo worms and so on until animals such as young Water Dragons are reached which will happily eat medium crickets and regular mealworms from day one.
Just as with the amphibians the food size increases as the animal grows - and initial growth is extremely fast. With most species I find that it is best to moderate the regime of "all they can eat" by the time they are about three months old or have doubled in length. At this stage in their life they should start growing more slowly and receive a higher proportion of carbohydrate (and for herbivores/omnivores a significant amount of vegetable matter).
With these techniques, maturity is reached much faster than in the wild and so long as the dietary switch is implemented with no adverse effects on life span. Continued intensive feeding at the high levels used in the initial growth stages after the initial fast growing period will often produce animals with fatty deposits, health problems and shortened and possibly unproductive life spans.
Use the menu (The animals) above to learn more about the species I keep or have kept.