Abstract The adsorption behavior of methylene blue dye, Bismarck brown Y dye and Indigo dye on to Sphagnumcymbifolium (moss) and Cedruslibani (Elizabeth leaf) were investigated as a function of flow rate, and bed height through the fixed bed process. OBJECTIVES: One of the main objectives of this research is to expand the field of application of natural biomass for the treatment of dye waste waters from industrial effluents. Also, it is aimed at achieving a comparative elucidation of the dependency or otherwise of flow rate and bed height on adsorption through the fixed bed technique using two different biomass. METHODS: The two biomass were characterized by scanning electron microscope (SEM), in order to examine the morphology of the two biomass. The screened biomass samples were characterized at 1000x magnification and 500x magnification respectively for their surface morphologies. This was done using a scanning electron microscope (FEI- Inspect/ OXFORD INSTRUMENT- X- MAX) which was equipped with an energy dispersive xray (EDAX) spectrophotometer employed for the elemental composition analysis. It was equally characterized with Fourier Transformed Infrared spectroscopy (FTIR) before and after adsorption to ascertain the functional groups responsible for the adsorption. This was done using a Fourier Transformed Infrared (FTIR) spectrophotometer (Perkin- Elmer, England) in the wavelength range of 350-4000nm. RESULT: Results for biomass morphology obtained through the scanning electron microscope (SEM) revealed the presence of tiny pores. These pores were more pronounced in the Sphagnum cymbifolium(moss) biomass than in the Cedruslibani (Elizabeth leaf) biomass. These pores represent sites where dye molecules could be trapped in the course of the adsorption. The results from the Fourier Transformed Infrared spectroscopy (FTIR) for both biomass after adsorption show that C-H, C?H and C?C functional groups were responsible for the adsorption. With the Sphagnum cymbifolium (moss) biomass, for methylene blue dye at the flow rate of 20m3/s, the amount of dye adsorbed was 18.80mg/g, 22.70mg/g at 30m3/s and 25.40mg/g at 40m3/s. For Bismarck brown Y dye, at the same range of flow rate, the amount of dye adsorbed ranged from 12.34mg/g-20.62mg/g. For Indigo dye, the values obtained ranged from 6.48mg/g – 17.71mg/g. In addition, at the bed height range of 4.0- 6.0 x 10-2(m) the amount of dye adsorbed ranged from 6.31mg/g – 27.73mg/g for methylene blue dye. Within the same range of bed height, the amount of dye adsorbed ranged from 16.40mg/g – 25.60mg/g for Bismarck brown Y dye and 12.57mg/g – 17.71mg/g for Indigo dye. On the other hand, using Cedruslibani (Elizabeth leaf) biomass, for methylene blue dye, at the flow rate of 20m3/s, the amount of dye adsorbed is 8.40mg/g, 11.30mg/g at 30m3/s and 13.64mg/g at 40m3/s. For Bismarck brown Y dye, at the same flow rate, the amount of dye adsorbed ranged from 4.71mg/g – 9.78mg/g. The values obtained with Indigo dye ranged from 2.80mg/g – 8.00mg/g. In addition, at the bed height of 4.0 – 6.0 x 10-2 (m), the amount of dye adsorbed ranged from 5.15mg/g – 24.62mg/g for Bismarck brown Y dye and 5.66mg/g – 14.86mg/g for Indigo dye. CONCLUSION: From the results obtained, it is clearly seen that methylene blue dye was the most adsorbed, while Indigo dye was the least adsorbed within the same flow rate and bed height ranges. In addition, the three classes of dyes used in these investigations which represent cationic, anionic and neutral dye molecules can adsorb on to Sphagnum cymbifolium (moss) andCedruslibani (Elizabeth leaf) biomass at various degrees. The amount of dye adsorbed is dependent on the flow rate and bed height within the range of experimental consideration. Furthermore, Sphagnum cymbifolium (moss) adsorbed better than Cedruslibani (Elizabeth leaf). In each of the analyses, three different experiments were performed and the mean values reported with their standard deviations.