Moving my 210g, do I need to keep the old water?

I am in the same boat as you j...I was thinking of using the 30 or some odd gallons I am going to transport the fish in as the first bit of water I add to my tank after it is moved, then adding new water and all established filters. Also I was going to put all my media in the transport bin in bags so it doesn't dry out and the bb stays alive.

You will just need to acclimate the fish to the new tank; don't just dump them all in as soon as you fill it. If you keep the old water, it will be less stressful for the fish. Probably not vital though.

what I did was fill my tank with new water, then acclimate my fish from the old to the new. It's like a free water change!

I've always just filled a trash can with old tank water, tossed in the fish there, then just pulled hobs moved tank dump in old water and fish then topped off.

Never had any troubles..... Moved 3 times in the last year and a half.

Test the water that you currently have in your tank and test the tap water where your moving to. As long as the pH isn't too far out of whack, you'll be fine. Transporting the water isn't necessary. As long as you keep the media in your filters submerged, your BB should be fine. Sounds like you're planning on doing things the right way. Good luck with that move, ugh! I don't envy you at all!

I'm not saying take 200 gallons of water....LMFAO

I'm saying take enough water to transport the fiches.....Dump the water and fiches all together into the empty tank....then top off.

I use a rubbermaid ag vat when I move. Throw it in the back of the truck back the truck up to the door and pump water into the vat. Fill trash cans with water and fish then
if I need more water then whats in the cans I just pump from the vat.....IF I don't need it then the new place gets its first yard watering.

Another thing I learned real fast when having to move 6foot tanks solo is that PVC is your friend. Get like 5-6 pieces 2-2.5 ft long and just use them as rollers. Helps to have a lil minion pick up the rollers you rolled over and place them in front of the tank.