You'll be looking at at P.senegalus or P.palmas polli simply do to the size of the tank.As for how many?It depends on what elsenyou want in the tank? you can easily do 2 without crowding 4 would be your maximum.
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.
BICHIR BIOTOPES
African River
West and Central Africa are full of rivers. Within each of these river systems are
numerous biotopes -- this description will focus on species found in slow-moving
sections and side streams.
WATER:
pH 6.9-7.2,
3-8 dH,
temp;75-81F (24-27 C)
TANK:
The tank should be furnished with wood for hiding places, and fine gravel or sand for a substrate.
The lighting should be muted, and the water should have a slight current.
PLANTS:
Bolbitis heudelotii , Anubias, Vallisneria, Eleocharis.
African Swamp
The waters support a variety of species and vigorous plant growth making it an ideal subject for a biotope aquarium.
Reedy plants line the shores of waterwaysWATER:
pH 7.2-7.8,
2-8 dH, 7
Temp:70-75F(21-24 C)
TANK:
The tank should have fine gravel, sand, or clay for a substrate.
Dense vegetation and floating plants help recreate the natural setting.
Use submerged wood to provide hiding places.
The lighting should be bright and the water should be clear.
PLANTS:
Bolbitis heudelotii, Ammannia, Marsilea, Eleocharis, Anubias, Nymphaea, Water
Lettuce-Anne
