Biodiversity of lentic habitats in river channels generally depends on a frequency of connection with channels and the time since the habitat was born. The Tagliamento River in the north Italy has a steep basin with high sediment supply and thus its middle reaches form braided channels changing frequently with flow fluctuations. To understand relations of species diversity of aquatic animal communities to age of lentic habitats, the temporal dynamics of the habitats in two reaches of the river were recorded by fixed cameras installed on the cliff tops beside the reaches. A total of 89 habitats were chosen to collect aquatic animals and to measure environment factors in April to May, 2011. This paper revealed that lentic species increase with the age of habitats while lotic species decrease with the age. Considering with specificity of habitat preference, we discussed on the age and longevity of the lentic habitats required for maximize biodiversity of habitats scale and reach scale.