The Fluval canisters are ordinary 88G paintball tanks. The labeling is a plastic shrink sleeve shrunk onto the canister.
It seems that 100% of the 88G tanks are made with that thread. At least the sites I visited said so.
There seem to be some manufactures that play loose with the length and finish of the threaded neck which makes for compatibility issues.
If you read the Fluval instruction sheet they make oblique mention of this.