Shari, Thanks for the thoughts--I always appreciate thoughtful suggestions and advice! Given your book

it's easier for me to comment and ask questions below--IN CAPS:
1. Wash your sand. 5 Gal buckets outside is easy, but prepare for a lot of water running. Mud. There will be mud. Unless you have a patio/deck or someplace without dirt by your hose. Stir and rinse till clear, then drain and move the clean sand into a moveable size container. Covers are good, esp if it will sit in a garage or outside. Don't want junk getting in it.
This is also a good time to test (on a level space) your 75 for leaks, and to wash it out.
100 LBS OF COLORQUARTZ SAND IS ALL WASHED AND WAITING IN LARGE COOLERS (WITH TOPS!). I HAVE A LARGE PORCH, SO NO MUD PROBLEMS.
THE 75 DESTINATION TANK *HAD* BEEN MY HOLDING TANK MOVING MY SW TANK INTO MY NEW 125--SO IT HAS NO LEAKS--JUST NEED TO CLEAN IT, THEN MOVE IT BACK IN AND LEVEL IT
***I WILL *NOT* BE CONTINUING TO USE THE OLD GRAVEL NOW THAT I HAVE THE NEW SAND*
2. Set up your 20g today or tomorrow and add some biomaterial from your running filters, either a sponge, or a bag with substrate, a few pieces of decor, but no loose gravel. Do you have plants? How much of your 46g decor will fit in the 20? If it will all fit (temporarily) move enough of that out to the 20 to make things cozy in there and keep the remaining stuff in the 46 till the day of the move. Get the temp stable and make sure it has a good cover. Can you move the 50 or the 70 over directly, or do you have another filter you plan to use? This way your fish will have an established place to be, temporarily, and you won't have to worry about buckets, air stones, heaters etc all over the place. Test the water for temp, chemistry etc. If ok, move a couple of small fish in right after set up, then do the rest of your prep work.
*MY MOVE WILL BE HAPPENING SATURDAY--ARE YOU SAYING SET UP THE TANK NOW *AND* START MOVING FISH NOW, OR WAIT TO RELOCATE FISH TO 20G UNTIL DAY OF THE MOVE?
I CAN SET THE 20G UP. THE BIOWHEEL FROM MY PENGUIN 20 HAS BEEN IN MY 46G FW TANK FOR OVER A WEEK, SO SHOULD HAVE A DECENT AMOUNT OF BACTERIA. I HAVE 4 FILTERS TO DO ALL OF THIS---2 OPERATING ONES (AQUACLEAR 70 AND EMPEROR 50); THEN BIOWHEELS FOR PENGUIN 20 (FOR QT) AND 2 BIOWHEELS FROM BIG OL' EMPEROR HAVE BEEN IN THE WATER IN 46G 7-10 DAYS, SO SHOULD ALSO HAVE SOME DECENT BACTERIA IN THEM. THE EXTRA BIOWHEELS HAVE BEEN STUCK IN INTAKE OF POWERHEADS, SO THEY ARE GETTING GOOD FLOW.
THE 46G HAS 2 LARGE PIECES OF DRIFTWOOD AND MAYBE 10 FAKE PLANTS, AND A GERBIL TUBE THING. ALL OF THAT *SHOUD* FIT IN MY 20G LONG.
I WILL BE MOVING DIRECTLY OVER THE FILTERS FROM THE 46G TO THE 20G HOLDING TANK/QT DURING THE MOVE.
I HAVE AN EXTRA 32 GALLON TRASH CAN I'LL BE FILLING UP MORNING OF THE MOVE AND ADDING IN A POWERHEAD FOR OXYGENATING THE WATER AND A HEATER TO HAVE TEMPS MATCHED.
3. Make sure you have a place out of the way to put the 46 when you take it down. And a place to put your equipment. If your heaters will fit into the 20 while your setting up the 75 that would be a good place to move them to. Turn them off a bit before you move them so they are not hot when you take them out of the water. You don't turn them on in the 20, they just sit there to keep the right temp for when you move them back over to the filled 75. Are you keeping any of the gravel from the 46? If so, you need a clean bucket for the removed gravel.
The day of the move:
1. When you are ready to take down the 46 put the rest of the decor from the 46 either into a bucket or the 20. Take out half the water and discard it. Move the remaining fish into the running 20. Yes, it will be crowded. However, it's not like an unfiltered bucket, and they won't be in there long. With an established filter running on the tank they should be fine for several hours. You will be moving most of the stuff back out of there to the 75, right?
YES
The moved fish will appreciate the multitudes of hiding spaces while they are in there, and you can leave the bumpy clown behind to use the 20 as a qtank, unless you already have one set up?
NO QT YET--THAT WILL BE THE 20G WHEN I SET IT UP.
2. Take down the 46. Remove all equipment (store filters in buckets or your coolers with some water), substrate, and water. Move the tank out of the way. Backyard is good. You can rinse the tank out later before you move it to it's final resting place.
3. Move in the cleaned, and tested 75. Level it! Have your needed equipment in a space out of the way, but accessible. First thing I do is add the substrate, then cover it with treated clean water till about 1/4 - 1/3 full (or more if you can't start a gravel vac). Stir the sand and make sure it settles down with no air pockets. There will be silt on top of the substrate. Vac it up, and refill part way with clean, treated (tank temp) water. When you pour water into the tank, put a plate or something on the sand and pour over/onto that. It stops the water from blowing the sand around. Make sure you don't fill it too high. It's easier to aquascape if you're not up to your armpits in water.
OK--THE SILT YOU MEAN IS THE DUST BECAUSE THIS IS NEW 3M COLORQUART SAND--CORRECT? BECAUSE I WILL *NOT* BE USING THE OLD GRAVEL CURRENTLY IN THE 46G.
4. Aquascape the tank while it's part full. Add your decor, plants, whatever. Fill with tank temp water (not quite full), check for air bubbles in the substrate, poke around to make sure there are none, let settle, and vac the silt out again. You can skip this step if you don't see silt settling all over the surfaces.
OK
5. ALL OK
6. Since you've taken most of the stuff out of the 20 (I'm assuming), it's time to catch the fish. Sometimes that's easiest if you remove some water first. As far as moving the fish themselves goes, the most important thing to me is matching the water, and minimizing stress. Be as gentle as possible. Net them from one tank to the other if they are close by,
THEY WILL BE IN SAME ROOM, PROBABLY 25 FEET AWAY. I WAS THINKING NETTING TANK TO TANK WOULD BE EASIEST.
if not, half fill a clean bucket with water from the 75, and water from the 20. Net them into the bucket, bring the bucket to the 75 and net them (or pour them very gently into the 75. Put on the cover. Leave the lights off. Watch the tank to see how the fish settle. Then, go back to the 20, refill with clean, treated water. Leave those lights off too.
Don't feed them till the next day and feed lightly for several days.
7. Clean up.
8. Think about how to treat your clown. If he's not too bad off, give him a day after the big move before you start treatment.
WAITING A DAY OR TWO PROBABLY A GREAT IDEA. WHILE HE HAS LOOKED WORSE OVER PAST 6 WEEKS, HE IS STILL BIG AND FAT, BEHAVIOR AND EATING ARE GOOD. I'M STILL NOT SURE ABOUT MEDS AND DOSING--SOMEONE RECOMMENDED MARACYN I AND II--CAN I DO BOTH AT SAME TIME, AND IF SO, WHAT DOSAGE?