For newt's photo I use a numeric camera (nikon D100) and a special macro lens but
the most important for the photo in tanks, it's a good light.
It's easier to use flash for that.
You can use two flashes (One on each side of the tank) or only one flash
with a wite reflector.
Photo with a small tank, one flash and a reflector:
Two important details, the angle between the tank and the flash must be 40°
and you must pass the lense in a dark piece of cardboard to avoid reflections.
Photo of the black cardboard:
I use different small and flat special tanks I only make for photo (it's easy to make).
Photo of the different tank:
The glass and the water must be really clean.
The water must be the coldest possible for the triturus, if the water is not cold, they don't like that, they are very nervous and try to escape from the tank.
I hope this answer a few to your questions.
JP.