whats the best and safest way to switch tanks

[Poor Boy]

Ill be upgrading my 30 to a 45 possibly this weekend.

[alton]

Watch the temp on the water, and make sure you have enough containers for water, rock, corals, and fish. A very large ice chest with a bubbler works great. Depending on the age of the sand you may want to use all new.

[OrionN]

Is it going to the same place?
Do you have any sand?
The best think is to remove the rock and fish in a large container with circulation and heat. Then move the old tank out and put the new tank in. rearrange the sand and rock fill it up and let everything running and heat up before release the corals and fish back in. With minimal time out of water, the rock should not recycle. Moving sand is different. I often just discard the old sand. You will have a cycle if you sand have a lot of stuff in it.
Make sure you have plenty of premixed salt water. Most of the time I do at least 50%+ water change with these moves.

[Justin]

I agree with Orion. I would go grab at least one or two Brute trashcans and use the wheel mounts to make it easy. Put your rockwork and frags in one with water and fish in another. Leave about an inch of water left with the old tank and sand if you have it. I would keep probably about a cup or two of this old sand and put it in a bucket or something to help restart the new tank. The rest I would just toss or use it for arts and crafts. This last inch is what holds all of your nitrate and phosphates and if you use it, you will most definitely cause a major spike in your parameters and kill quite a bit due to the shock. Keep temp stable and when you are ready, work in reverse adding the stuff to the new tank. First the rock with frags in it, then the one with fish and the rest of the water. Take about 10-20% water change with the old water and add new stuff to your new water level of the new tank and you should be fine. Take your time adding the livestock as they will be in a little bit of shock due to the move. Ideally, you want to space this out over time and not rush it. Just make sure that temp is constant and you should be fine.