I had a question about whether they should purchase a new tank or an old tank. Everyone loves new, but can you go old too?
From a looks perspective, you may notice unsightly water marks as minerals may be deposited on the glass. This can be easily cleaned off using warm water or dilute vinegar. Don’t worry about light scratches on the tank as they will look invisible once the tank is filled.
From a disease point of view, if the old tank is dry and has been out of circulation for several months, then there ought to be no issues. If in doubt, you can always disinfect with chlorine/bleach and then make it fish-safe again by thorough rinsing and by the use of dechlorinators.
From a practical perspective, you cannot be sure whether the tank will hold up or leak, especially if the tank has been dry for some time. Thus, it is always best to fill the tank in stages. Day 1, fill it to 30% capacity. If no leaks, then fill it to 50% capacity on Day 2. On Day 3, it might be safe to fill it to the maximum water level. Leave it for a week at least prior to stocking the tank.
Biologically, when moving fish from their old tank to their new home, make sure you use as much of the old tank gravel, water, furnishings and filtration equipment to avoid bringing about ‘new tank syndrome’. See fact sheet entitled “Ammonia, nitrite and nitrate” at http://thefishvet.com.au/fact_sheets.html
