Also, as you have posted this in the brackish forum, (which is great for f8s) I feel obliged to mention that ceylons are freshwater puffers. But you knew that, right?

Not without breaching the rules of this board by directing you to two other forums, one which specialises in Puffers and one that's all about Oddball fish.

Ok, on reading more about Ceylons, it seems that although they are often sold and kept as freshwater fish, they do actually do best in brackish water.

We get most of our info from a book called The Puffers of Fresh & Brackish Waters by Dr Klaus Ebert and published by Aqualog. Dr Ebert has been keeping puffers for over 40 years. He knows what he's talking about.

Here's the basics:

<span style='font-size:14pt;line-height:100%'>Celon puffer</span> Tetraodon Fluviatilis (Asian)
Other names: Green puffer (not to be confused with the greenspot), Sri-Lankan Puffer, Bengal Puffer.
Variants & confusions: Available in two forms, one that's easily mistaken for a figure eight puffer, and one that looks like a dull greenspot.
Size: up to 7.5 inches.
Water: Most commonly kept in fresh to mildly brackish water, but is also happy in water right up to full marine.
Temperature: 22 to 25c
pH: No special requirements, 6.5 to 7.2
Light: Not too bright
Food: live foods, molluscs, shellfish, insects.
Decor: Likes live plants (java fern only in brackish water)
Temperament: tolerant of others of the same species, but will eat other fish smaller than its self and eat the fins of larger fish.