I have read promising articles about the (new) 18-55 f/3.5-5.6 IS and the new 55-250 f/4-5.6 IS. I have no personal experience with either one but things are looking up. If you aren't sure whether this photography stuff is something your going to really like, or if you just don't have the money, I would think the 18-55 f/3.5-5.6 IS and 55-250 f/4-5.6 IS route would be just fine. If you are going to use your camera on a regular basis, you likely will soon desire something better and wish you had gotten a 70-200 to begin with.
Now the 55-250 f/4-5.6 IS has some reach, but it will need lots of light to feed that hungry aperture. This lens would be a poor performer indoors or early morning/twilight. You will need to be outdoors in bight sun or otherwise use a powerful flash (such as the 430 ex II or 580 ex II...not the one already on your camera) for acceptable results.
From what I have read, I would endorse the 18-55 f/3.5-5.6 IS and 55-250 f/4-5.6 IS to get you started. As you gain valuable experience with these tools, you will build an education and learn for yourself why you need anything better (if) you need anything better. I would not recommend either of these for reef photography however. You should include the 100mm f/2.8 Macro lens in your budget for your tanks as well.