Hello All - New member

[albert_dao]

Sorry, I typed that last response with one hand (pizza in the other).

Here's why you don't want to use old water:

1. It is heavy as f***.
2. Salt is pretty good nowadays. As long as you premix it to the proper temp and salinity (use a refractometer), your animals will welcome the change.
3. When you uproot your tank, you will inevitably allow all sorts of nasty wastes and metabolic byproducts into the water column.
4. Bacteria don't just float around in the water column, they are in your rocks.

As far as substrate goes, just get new substrate. Don't use too much. 1-2 cm of a clean coarse gravel will do. I prefer 5-7 mm grain size. It allows you to max out your flow without making sandstorms and is easy to gravel vac.