From the primer in the sticky section
Water chemistry
In their natural occuring range West and Central African rivers,lakes and swamps
bichirs are found in water conditions varying in pH values between 6.5 to almost 9.0.
And water hardness varying between2dH to almost 20dH.
And tempuratures ranging from mid 70'sF to mid 80'sF
with a dissolved oxygen content between 3.3 parts per 1000 by volume
and 2.50 parts per 1000 by volume.
3.3 parts per 1000 by volume is common in aqauria kept at 75 F
These water parameters will flucuate thruought the year as dry season gives
way to the rainy season and rivers rise and swamps flood often lowering water temps
for short peroids of time.As you can see they are tolerant of a wide range of water
conditions.
Brackish bichirs?
Bichirs are freshwater fish and, though some are found in rivers near where they empty into the ocean, the water they inhabit is fully fresh.
Polypterus ornatipinnis and Polypterus e.congicus are sometimes found in Lake Tanganyika which has hard, alkaline water but are rarely, if ever, found in the lake itself. Instead, they inhabit the swampy areas where river water empties into the lake proper.-Anne