Hello Fat Homer! Nice to see a fellow fat guy
I don't have G. Polyuranodon yet, still in the process of acquiring one. All the G. Polys you see in this thread, all belonged to Mr. Septian.
Most of the Indonesians I know who keep G. Polys, Strophidons and E. Rhodochiluses, keep them in freshwater.
I do have three cute Echidna Rhodochiluses, I keep them in a low-end brackish aquarium (1 part seawater, 5 parts freshwater, with fluctuating salinity simulated by alternating between swapping seawater and freshwater during routine water changes).
This is my largest E. Rhodochilus, I call it Mr. Emerson.
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