Help me shoot my fish

I heard somewhere that to shoot a fish tank to use the slave to the side or above, and I get that, it totally makes sense, but my problem is getting bounced light from the camera flash off the glass. I heard that the flash triggers the slave and that it doesn't give off light to the subject even though it flashes is this true? Yes, I have it set to slave only in the setting mode. Maybe I'm just not reading something right or what do I need to adjust? Sorry I guess I should have said I have the 60D.

I have never tried shooting with a flash. As long as the light over the tank is adequate. I just bumped the ISO up. I think there may be some reflection issues. Tried that through glass shooting a bird and it just did not work. Unless someone knows better I'd try without a flash first.

You need a fast lens to start with. No flash is needed. Here are some tips.

http://www.slrphotogra​phyguide.com/aquarium-photography.shtml

Macro shots of fish?