Hi there
Green tree frogs will regularally turn brown,
many say they are stressed but they are
either cold or resting usually
i would say that green tree frogs do need lighting for natural day, night tine cycle. i use a 50 watt tropical heat
bulb and/or UV bulb that is 50 watts, if the frogs are continuously brown all the time, try a dimmer light, there are
a couple mad by fluker's and exo terra.
For the water dichlorinator, ive only used exo terra and Zilla dechlorinator, ive never had this sort of film residue
on my reptile dishes but it is normal for a small amount of bubbly foam to be on the surface of the water.