So I'll splain a little more since the roast is now in the crockpot. First, the other lens that comes with the original kit, (I'd imagine it comes with a 18-55 or 18 -120 or something like that), would be better for shooting your tank or shooting landscapes. For some reasons, I'll say partly because of "minimum focusing distance". The 18-55 will be somewhere in the few inch range, the 70-250 in the few feet range. Trying to get pics of a tank will want you to be as close to the glass as possible. You may be able to add "extension tubes" to get closer, but the inherent problems of having cheaper glass in a kit lens will show, (though that is one of the less expensive ways to go).
Most of us end up with "true" macro lenses for shooting the tank. Most of the close-ups you see on here are shot with these. These are prime lenses, (only two exceptions I can think of), which means they don't zoom.
Now you should know I'm speaking from the Nikon side. I can't say much about specific Canon lenses, though I do know, you get what you pay for. Bill above shoots with Canon, IIRC, but I also have an old Sigma 50mm macro in my collection. It's a wonderful lens. Photography is a lot like reefing. Sooner or later, if you stay with it, you'll buy better lenses. Visit the photography forum. We play games to help people .
