Awesome advice. Thanks Diana! I REALLY appreciate the level of detail. I started the deep clean process with my water change today and am going to decide on what size to go with. The 55 just doesn't have the depth I want in order to have a proper background to foreground 'ratio', if that makes sense.
PLUS, and this is daddy's fault, I left the magnetic scrubber attached to the tank one afternoon and the kids decided to help me clean. Well, they dug into the EC and brought up some nice sharp grains and did one heck of a number on my tank walls. I mean REALLY bad deep scratches. It looks like crap. That tank will probably be a grow out/holding tank for shrimp and plants trimmings to sell on eBay or something so I can subsidize the upgrade to the larger tank, filter and light. Ah the circle of life!
EC is great for many years, never wears out.
It can hold fertilizers in a way that plants can use them, but it is not a fertilizer itself. Nitrifying bacteria live on all the surfaces of the EC, where ever there is good water movement to bring them ammonia and oxygen. Generally this is the upper layer of the substrate.
I would do this:
Get all the new equipment (filter, heater, lights... whatever you have in mind) and test it ahead of time.
Do a few deep vacuuming jobs on the substrate over a week or two.
Clean the current filter media.
Prepare enough water for a 100% water change.
The day of the move:
Turn off, unplug, remove all equipment.
Drain the best water into as many buckets as needed. Put shrimp, fish, plants and rocks in the buckets. Cover the buckets. Fish and shrimp can jump. Dark is less stress for the fish. Large driftwood could lay on some garbage bags. Careful: there will probably be some shrimp clinging to the wood. Do not put too many fish or shrimp in one bucket. The shrimp will be best with something to cling to, like some plants or a nice branchy piece of driftwood.
If you want to treat the plants for algae or snails this is a good time to do it. You could add something like hydrogen peroxide or Excel to the plant buckets in doses that the shrimp cannot handle, then rinse before planting them in the new tank. There may be shrimp clinging to the plants, too, so try to remove them before treating the plants.
The filter media with the nitrifying bacteria should be kept damp, but does not have to be under water. High oxygen is important.
Skim the top layer of substrate (not even 1/2" deep) and save this. This is the part that is the richest in nitrifying bacteria.
Use the remaining water in the tank to do more cleaning of the substrate. The more gunk you can get out now the less cloudy the new set up will be.
Set up new tank and equipment, putting the old media into the new filters. If it does not fit, then hang onto it, put it in a mesh bag. This is the richest source of nitrifying bacteria.
Put old substrate in the tank, add fertilizer (tablets, powders... whatever is needed) in this lowest level. Do not use the reserved substrate that is the richest in bacteria yet. I am assuming you are keeping the EC and adding more, depending on the footprint of the new tank.
Put the new substrate on top of this.
Arrange hills and valleys, add rocks, driftwood... Be careful not to disturb the fertilizer.
Add just enough water so the lowest spots might show a little bit of water.
Plant. Mist the plants often.
Use the reserves substrate like a cap. This places the maximum nitrifying bacteria right back into the best oxygen area.
Put a piece of plastic or a plate over the substrate and fill slowly, allowing the water to seep over the edge of the bag. This will minimize clouding. If you want to boost the population of nitrifying bacteria add a product that contains Nitrospira species of bacteria. Do not waste your money on anything else.
Turn on the equipment when the tank is full enough, and make sure it is all working.
If the old media does not fit in the new filters hang it in mesh bags (about 3-4) in an area of good water flow.
Add the livestock. Do not add the water the fish were in. When fish are stressed they add excess ammonia and stress hormones to the water. I do not know about shrimp.
The rest of the day: Lights off. Do not feed.
The next day and beyond: Lights on, feed, but maybe only half the regular amount. Check for ammonia, nitrite. Be ready to do a water change if needed.
If no ammonia shows up, and the livestock is acting normal, then go ahead and feed the regular amount.
About once a week remove the old media that was hanging in mesh bags.
You might back off on the fertilizer (if you dose the water column) until the plants are settled.