Here is a fun idea for you to try if you have not already.
Buy a fresnel lens at least 4x in power you can see one.
!!HERE!!
I think that link is ok. very sorry if its not.
Tape it up to your tank then take picture through that.
Also put you face right up against it and you will feel as if yout inside you tank. It makes it look VERY deep and almost 3D like. you will see some amazing stuff you never saw before. if you have ever used a magnifing glass on you tank that is nothing compared to using these lenses.
you can find them in all size and shapes but they can get REALLY high up in cost. a basic 8x11 Fresnel 4x lense should be around 5 bucks at a local old people store lol. Be sure to get atleast 4x