I just went through this exact situation 6 weeks ago. I had no losses. The tank didn't even cycle.
I had found an established FOWLR tank for sale about an hour away from where I live. So needless to say, I had to complete the whole move in one trip.
I will tell you this now... Put aside a WHOLE DAY for this. I arrived at the guy's place at 8am, and only had all the livestock and everything else in the tank at my place at 8PM.
First things first. FIND NEW SAND. I doubt you will be able to use the current sand in the tank since by stirring it all up, you will loose the gas exchange that has been established in the sand, thus the tank WILL cycle. You can't move the tank with the sand in-tact, since it will be too heavy, and it will get stirred around in travel anyways.
The person I bought the tank from was using a CC substrate with a plenum. I knew that I was going with DSB anyways, so I bought 160lbs of playsand, and 40lbs of livesand since I wanted a 5" DSB in the 90 gallon tank I was buying. Your application may vary.
Preparation:
-Get your new sand and have it ready at your place.
-Since you're buying a 58 gal, have atleast 50% of that (29gal) of water mixed and ready with salt. (mixed 24-48hrs earlier). This is incase you loose water during the trip (it happened to me), and in the worst case, you'll have more water ready for anything.
- Buy 3-4 Rubbermaid containers with covers to transport the LR and other inhabitants. Keep rock only with rock, and have a rubbermaid used ONLY for the fish, inverts, etc.. Use dark rubbermaids so as not to stress the fish.
- Buy 4-5 5Gallon water jugs (like the ones used for water dispensers). These work great for transporting the water, and work great for storing water afterwards.
- Have the space ready to accomodate the tank. Make sure you have a power source near the intended tank area, And have plastic bags covering the general area where you will be installing the tank. Handling so much water, there WILL be some spills.
- If you don't have a truck/van, you will need to rent one so that you can do this in ONE trip.
- Get Beer... You will need this for later on.
- Hire 1-2 friends to help you out.
Starting the move:
-start by removing the LR and putting it into rubbermaids. If you bought 4 rubbermaids, use 3 for the rock, and 1 for the fish. As you finish with 1 rubbermaid, siphon water from the tank into it to keep it submerged.
-Once all the LR is out of the tank, you'll notice that there isn't much water left. And now you can catch the fish much easier and put them into the remaining rubbermaid, which ofcoarse has tank water already.. Half full should be more than enough for this rubbermaid. I used a small jug to catch the fish and put them into the rubbermaid.. I think that nets can/could do damage to a fish, let alone add stress.
-Siphon the remaining water into the water jugs that you bought just for this occasion. Try to leave about 1" of water over the sand so as not to siphon any sediment into your jugs.
-The remaining water should be siphoned and disposed of. By this time, things will be starting to smell.. Algae on the glass will be dying off, and things will now get smellier.
- Now the fun part. You will have to scoop out the sand (USE GLOVES HERE), and dispose of it in industrial strength garbage bags. This is a SMELLY stage of the move. Once it's all out, lift the tank off the stand, and take it outside for a final rinse with a garden hose before packing it up.
- a note on filters.. Keep any filters submerged in tank water, and/or fluval's full of tank water. This will prevent the good bacteria from dying off.
- Pack it all up, and move FAST. Try not to do any suddent movement while driving, since the water WILL slosh around at the slightest movement.
Unpacking:
- Start by taking the tank out, giving it another rinse, and now scraping off any dead algae, coraline or otherwise. Have the tank looking new when you install it.
- Install the stand, and then the tank into the spot you cleared out earlier.
- Take one of the powerheads and a heater, and put it in the rubbermaid with the fish/livestock. This will help them for the time they have to spend in there.
- Now the sand... You will have to rinse the sand before you put it in the tank to prevent it from clouding up. This does NOT apply to the livesand. Normally sand bags come in 40lbs bags. Empty the sand into a large container, and rinse it outside with the garden hose. Basically put water into the container with sand, and with your hands move the sand around... pour out the cloudy water and repeat 3-4 times until the water is pratically clear.
- Put the rinsed sand into the aquarium, try to lay it out flat along the bottom. Once all the PLAYsand is in, put in your LIVE sand as a "topcoat".
- Now it's time for the water. place a bowl on the sand and slowly add the water you brought in the jugs from his place onto the bowl in the aquarium. By pouring the water on the plate, you won't displace the sand in the aquarium.
- Start adding rocks when you finish with the jugs. Add any remaining water from the rubbermaids into the tank as well. Arrange the rocks now the way you want them to look.
- Get the water movement, filtration, etc... going and let it go for an hour or 2 to let things settle in. Add any missing water from the prepared water you made before in the preparation phase top off the tank. This can be thought of as a small water change since you're putting in new water.
-Distribute Beer among hired friends. Maybe a pizza may be due here as well...
- If you had moved corals, introduce them now...
- If everything seems settled down, and there isn't much cloud left in the tank, you can start introducing your inhabitants. Using a jug, take them from the container, and pour them into the tank.
They WILL hide since they are scared from the ordeal they just went through. Install the powerhead and heater from the rubbermaid the fish were in, into the tank or sump (if yours came with a sump), and make sure everything's working.
- Keep the lights off on the tank until the next day to allow the fish to settle into their new tank environment.
I'm not sure if I forgot anything... But with enough preparation, you should be ok.. I suffered NO losses in the move, water params are perfect, and fish are now doing better since the previous owner had started to neglect them. There will be a period that the sand will mature (new sand syndrome?). During this time, the sand will have some algae blooms on it. Which will disappear...
Hope this all helps.