what kind of puffers?
There are many kinds after all, and each would warrant different regimes.
I keep 1 fahaka puffer and 2 figure 8s (not in the same tank)
I usually try and change 40% of the water a week for the fahaka, with spot checking throughout the week for detrius (geez he can be messy) and about 20% weekly for the fig8s which are in my brack tank.