First of all, before we get started it is highly recommended that pufferfish be kept in species only environments, meaning only having pufferfish in the aquarium.
There are a few reasons for this, as freshwater and brackish pufferfish can be a relatively aggressive fish, nipping at pretty much anything that gets close enough.
When it comes to competing for food they aren't very good at it, you can tell from just looking at them that they aren't built for speed and so getting a meal before other fish can be difficult without over feeding the entire aquarium.
Finally, pufferfish are a delicate fish, not suitable for beginners, they get stressed very easily and so the health of the fish can change quickly with small changes in the aquarium or fish that move too quick and bother the puffer. Taking all of this into account some people choose to not necessarily to ignore my advice but to try it in an aquarium anyway.
Over the years I've developed a list of the best additions that are less likely to cause problems. I have developed a method for doing this purely because of pufferfish popularity.
First, we must start with an empty tank, decorate it to your taste but with both lots of hiding place and also open space, bearing in mind that if you are going to go for a brackish puffer that plants don't really do too well with salt. Obviously allow the tank to cycle.
Add the fish you are going to house with the
I use around 1 tablespoon of aquarium salt to every 10 litres of water. It is crucial this part is done very slowly and properly. Now you can add your puffers.
Before choosing tankmates a question needs to be asked, do you want all the fish to exist peacefully? Clearly, this aquarium is tailored to the puffer, so would be ok to get cheap peaceful fish that your puffer might consume from time to time?
Bottom dwelling fish
It is important to have these as a primary tankmate to your puffers, they're not going to inhabit the same space and therefore can avoid the aggression and the competition for food, the next thing to consider is these fish need to be quite hardy to cope with the salt content.
1. Bumble Bee Goby
Upto 1.5 inches
2. Clown Pleco
Upto 5 inches
Although not a brackish water fish, I have myself kept sucker mouth catfish in a lightly brackish tank and they have thrived. The with clown plecos key is the slow acclimation process.
Upto 4 inches
Any of the Corydoras species will do here, they are a very hardy fish and one that I have again kept before with Brackish Puffers successfully.
Snails definitely need to go into a tank first and establish a self-sustained population, in a community, they will form the majority of the puffers diet as other fish won't eat these. Yes, other foods will still be given, to have as much of a varied diet as possible. Consider also these freshwater snails will not be high demanding with the other fish in the tank.
4. Pond Snails
Upto 1 inch
There is a great selection of pond snails on the market today, any of them will do to add in before the puffers, in a good tank they will soon thrive and colonise the aquarium providing a never-ending food source for your puffer.
5. Ramshorn Snail
Upto 1 inch
This is another quickly reproducing snail that will establish into a community tank. Much like the pond snails they are considered a pest in most aquariums yet here they find their place.
Peaceful community fish
The fish in this section aren't necessarily going to be a perfect match for your puffer, theirs no such thing, however, if kept correctly will not cause any harm to
Upto 4.5 inches
Mollies will always be most peaceful when kept in groups of 5 or more, they are a freshwater fish that if acclimated properly can survive a completely marine environment. If possible try to get these at a size that is just ever so slightly smaller than your puffer.
7. Neon Tetra
Upto 2 inches
Neon tetras can be found at any fish store, they are a very cheap fish. Neons are capable of quite easily out running and out manoeuvring a puffer and so can be kept alongside them. That is not to say however that a few may not get caught, the cheap price tag allows them to be restocked at no major loss to money.
8. Harlequin Rasbora
Upto 2 inch
Another peaceful, hardy community fish that is capable of withstanding forever changing brackish conditions. They are peaceful enough not to cause harm and yet again quick enough to move out of the way. Harlequins are another fish that is stocked in pretty much all pet stores and is again inexpensive.