Cells are rods approximately 3 µm long and 0.7 µm wide growing mainly as single cells. The optimum NaCl concentration required for growth is 0.045 % (w/v). Negative for catalase, oxidase, aesculin, indole production, nitrate reduction, urease reaction and gelatin hydrolysis. There is a positive reaction for α-galactosidase and 6-phospho-β-galactosidase, but not for β-galactosidase, arginine arylamidase, histidine arylamidase, α-glucosidase, β-glucosidase, α-arabinosidase, β-glucuronidase, N-acetyl-β-glucosaminidase, glutamic acid decarboxylase, α-fucosidase, alkaline phosphatase, proline, leucyl glycine, phenylalanine, leucine, pyroglutamic acid, tyrosine, alanine, glycine, glutamyl glutamic acid or serine. The cells grow well on YCFA-M medium. Growth occurs in the temperature range 20–28 °C (optimum, 24 °C), at a pH range of pH 6.9–8.5 (optimum, pH 7.8). The fermentation products produced during growth in YCFA-M medium are formate and acetate. Cells grow only under reducing conditions in the absence of oxygen. The major cellular fatty acids present (at >5 % of the total) are C14 : 0, C16 : 0, C18 : 0, C16:1n˗7t and C18:1n˗9c.

The type strain is strain BP52GT (=NZRM 4757T=JCM 34692T), isolated at the School of Biological Sciences, University of Auckland, New Zealand. Strains were isolated from the fermentative hindgut contents of the herbivorous marine fish Kyphosus sydneyanus.

Cells of the only described species are weakly Gram-positive (easily decolourized and may appear Gram-negative). The cells are rods (2.0–3.0 µm long and 0.7 µm wide) sometimes with one or two pointed ends. Colonies on YCFA-M agar appear white, opaque and shiny with a diameter about 1 mm after a week growing anaerobically at 19 °C. No endospores or flagella were seen. The type species is Tannockella kyphosi.