We report the generation of widely wavelength tunable conventional solitons (CSs) and dissipative solitons (DSs) in an erbium-doped fiber laser passively mode-locked by nanotube saturable absorber. The tuning ranges of CSs and DSs are similar to 15 and similar to 25 nm, respectively. In anomalous dispersion regime, the output CS exhibits symmetrical spectral sidebands with transform-limited pulse duration of similar to 1.1 ps. In the contrastive case of normal dispersion regime, the DS has rectangular spectrum profile and large frequency chirp, which presents pulse duration of similar to 13.5 ps, and can be compressed to similar to 0.4 ps external to the cavity. This fiber laser can provide two distinct types of tunable soliton sources, which is attractive for practical applications in telecommunications. (C) 2017 Published by Elsevier B.V.