Canon 300D, handheld
Sigma 24-135 at 70mm w/ 20mm extension
Canon 380EX off-camera
1/60 second, f16

Could have been better
So, here's the thing about aquarium photography. Since you don't want it to appear to be shot in an aquarium, and might perhaps be aiming at sales by showing a natural habitat, your choice of substrate material is important. Spotted salamander (Ambystoma maculatum) larva don't inhabit sandy bottoms all that often, and are found more among rocks, leaves, and mud. These, however, present not only numerous hiding places for such a subject, making it next to impossible to photograph, mud will remain suspended in the water for a ridiculously long time, and leaves must be 'conditioned' to serve as a bottom cover — dry leaves collected from the yard will float for days and probably appear too bright anyway. Sand, however, settles out right away, provides no hiding places, and is somewhat moldable. Since this was a temporary capture and I had no tank set up for sustainability, I did a few quick shots and released my subject back where I'd found it.

If you're planning to tackle this, keep a few choice, large leaves in a bucket ready for insertion as your bottom cover, and perhaps a couple of smooth river stones. To this, add a plentiful supply of patience.