Green Spotted Puffer
You don't say anything about the size or age of your puffers but I would go ahead and add a bit of marine salt. For instance if you do a water change of 5 gallons, add maybe a cup of salt to the 5 gal bucket being sure to mix the salt well. You can use a powerhead in a bucket and allow it to mix for a number of hours before adding if you would like. Buy a hydrometer also. You can keep these guys for a couple years at 1.006-1.010 but when they are say 3 inches or so you may want to begin increasing the salinity over time.
I have a gsp that is about 4 years old--he is at 1.012 and I am raising him to full marine salinity.
Another thing--you may be able to keep 3 of them in a 29 for a while but as they mature they may become very aggressive to one another. Mine lives alone in a 20 gallon high which is actually a bit small--he will be getting a new tank in the future. Puffs also require over-filtration and regular water changes as they are messy eaters and poopers.
