Advise with moving tank

If the tank has enough bacteria in the filters just use new water and treat it as a 100% water change.

plasti dip
idk about the water stuff, just add new water and use same filters. do not clean bb out of filter

what kind of fliter are you using? I just moved my 125 last month. Just keep water in the filter should be fine. I also painted the back of my tank black just use 2 cans of matte black spray paint

Acrylic flat black latex. As said treat water as 100% change

Water has no beneficial worth to the beneficial bacteria colony. BB that convert ammonia and nitrite stick on to surfaces and are not free floating thus you are just dirtying up your 125 when you save water. All the Bb is in your filters/decor.

If you do large frequent water changes and dont have sensitive fish then theres no benefit to saving old tank water. I personally do 80% water changes so when I move tanks I throw out all the old tank water and then add brand new water. My nitrates are always around 15-20 ppm so its not a shock to them. But if you have +40ppm then throw them into 0ppm water they will probably do fine. Fish adjust to nitrates within a period of roughly two weeks. Some weaker stressed fish could die as they then become too stressed but if your tank is healthy theres no need to save old tank water.