How to shoot through curved glass

[Ginu]

Hey guys, I have a simple question in regards to how to shoot through curved glass...

I have a euro aqua 34g tank which has the front of the tank curved and have a really tough time getting anything in focus from the front...
For camera equipment I have the following:
Nikon D90 - gripped
Tripod/monopod
18-200 AFS
70-300 VR
50mm 1.8 AF
28-70 AF
SB 600

I'd like to add that I'm not a beginner in photography, been shooting for years, however I hit a wall with this curved glass...

Any tips on how to shoot in order to help with the focus? I am eventually going to get a macro lens f2.8 60mm VR or f2.8 105mm VR however that's down the road as I don't have a single macro lens.

Thanks in advance