making pond bigger

im currently looking at making my pond deeper , i intend to remove fish and store them in old baths, once i have finished making pond deeper and fitted new liner , is the there any think i should add to the fresh water ie any type of solution or chemicals etc , and i long should i wait before i return fish back to pond , any help would be appericated

I think using the old water, making sure you have good circulation and maybe adding a bit of slime coat additive would be good. The fish will be stressed (anytime the environment changes). How long is it going to take to increase the size of your pond? Are you going to increase the capacity of your bio filters? How are you going to feed the bacteria in your bio filter if you have one? Also, if your increasing the size of your pond....are you adding a larger bottom drain (if having one).

Sounds like a fun project!!!

Cheers and Good luck,

Tom