I am using only macro mode from the camera without any addition lens. Place ur camera as close to the glass as possible. Use manual mode, manual focus, Speed 1/30 if ur hand is steady, smallest possible apeture. ASA 50 if possible, ASA50 has adventage when come to photo enlarge, croping and other editing. Remember ur len must be perpendicular to the glass to avoid distorted image if u are using 12mm thick glass.
To avoid other stray light, try to take ur photo at night when ur tank light is still ON. OFF all the light in ur room during ur photo session.
Hope this help...