Three new myxosporean species are described from Tetraodon fluviatilis (Osteichthyes: Tetraodontidae) imported from Southeast Asia to the Czech Republic. Zschokkella tetrafluvi sp. n. lives in the gall bladder. Di- or monosporic plasmodia produce ellipsoidal spores averaging 11.3 x 7.2 pm. Zschokkella pleomorpha sp. n. infects renal tubules and renal corpuscles; mono- to polysporic plasmodia produce spores averaging 15.7 x 7.1 pm. In the process of maturation, immature subspherical spores assume elongated shape. In both species, extremely curved suture line does not bisect poles of the spore. Ortholinea tetrafluvi sp. n. occurs as a rule in mixed infections with Z. pleomorpha sp. n. in the renal tubules. Mono- to polysporic plasmodia produce spores with a wide anterior and a narrow posterior end, averaging 8.3 x 7.8 pm. Both Z. pleomorpha sp. n. and O. tetrafluvi sp. n. have also limited number of stages located within the renal tubule epithelium, where they can complete sporogony. In one of the fish specimens, a myxosporean tentatively identified with Sinuolinea tetraodoni El-Matbou)i et Hoffmann, 1994 was found. A new genus is proposed for Ortholinea alata Kent et Moser, 1990 - Kentmoseria gen. n., and its diagnosis is presented.