Thought to share some pics with you.
For me the best ways to really make the tank stand out are:
Lay on the ground or on the same height as the tank anyway;
Use a telezoom lens. The lens is a Nikon 55-200 4.0-5.6 AFS VR, the camera is a Nikon D90.
I always use RAW but jpeg is fine too in most cases.
A tele compresses the view, making the tank more pronounced;
Get as close to the tank as you can and hold the background, in this case the trees, as far from the tank as you can, in this way the background becomes very blurred , thereby emphasizing the main subject, which is of course the tank in this case;
If your tank is brand new , like mine, desaturate the colors to make it more like a used tank.
Sharpen only the tank in post process, again making it more stand out; The Nik output sharpener is excellent for this and with it you can also unsharpen the background even more. you can legally download the whole Nik collection for free here:
https://archive.org/details/nikcollection-full-1.2.11
In case this does not work see how you can do it legally here: https://www.youtube.com/watch?v=UMyQMkIkx0k





In this picture I added a motion effect by using Nik Analog Efex Pro and choose 'motion unsharpness' under the tools menu:

If you have any questions feel free to ask! Regards, Bastiaan