I don't know about the Sony, but my guess is that technique is the issue.
First, get the tank ready - clean the glass and shut off all the pumps and wait a minute for things to become still.
Then, get your camera ready. Use a quality tripod and make sure your lens is perpendicular to the glass. I use a hood on my macro and usually have the hood right up against he glass to be sure I am straight which puts the lens back about 3".
Next, compose the shot. Use the self timer, a remote trigger, mirror lockup, or all of the above to take the shot.
For detailed shots, you need the subject to be still and the camera to be still because the shutter time will likely be pretty long for a decent depth of field. If that is not possible, you can take several pics with different focus using faster shutter times and look into focus stacking techniques.