Hi, welcome to puffers aquarium, here is a website for lots of different fresh water puffers..
http://www.thetropicaltank.co.uk/Fishindx/puffers.htm
The fresh water puffers are in the origin section and says '(FW)'.
These are 3 of the red eye puffers..
Carinotetraodon irrubesco - Red-tailed Redeye puffer Asia (FW)
Carinotetraodon lorteti Lortet's - crested puffer Asia (FW)
Carinotetraodon salivator - Striped redeye/Zebra puffer Asia (FW)
They all grow to around 2" (5 cm) also active fish, they say best not to mix but i think the first two top ones are fine with each other, however i'm not too sure so you will have to research that, or if someone else corrects me right on here.
I am getting the Carinotetraodon irrubesco Red-tailed Redeye puffer today later on, and she is selling to me 3 males and 3 females, and she said that they do completely fine together and no fights. Which i believe she is a expert as she is keeping 17 different species of puffers and with over 60 puffers in tanks, and to me that sounds like a real puffer fan lol.
Don't over stock with these though as some times they can fin nip, they say to have 1 red eye puffer every 5-10 gallons.
You could also keep a figure 8 puffer in there which they only grow upto 6cm generally in aquariums, they are also very attractive fish. Here is a website to help -
http://freshaquarium.about.com/cs/other ... puffer.htm
You may have heard people saying that brackish is compulsory however they have lived in fresh water and have been very successful in these conditions. They say 10 gallons minimum space so in a way you could keep 3 of these in a 29 gallon tank, When they are small it is best at 3 however fully grown best of 2 of them.
Hope this helps :p