Theoretical value of an aquarium...

[Samw]

I think it is much harder to sell entire systems and get as much as you would if you sold everything individually.

For individual items, as a seller I try to price my items like this: 90% if the item was never used. 70-75% if it was used less than 1 year. <60% for over a year.

As a buyer, if a used item was being sold for more than 80%, then I would prefer to buy new with warranty.