Blackwater rivers resemble clearwater rivers (such as [[Tapajós River|Tapajós]], [[Tocantins River|Tocantins]], [[Xingu River|Xingu]] and some right tributaries of the [[Madeira River|MaideraMadeira]]) in having a low conductivity and relatively low levels of [[Total dissolved solids|dissolved solids]], but clearwater rivers have water that at most only is somewhat acidic (typical [[pH]] ~6.5)<ref name=Duncan/> and very clear with a greenish color.<ref name=Giovanetti>Giovanetti, T.A.; and Vriends, M.M. (1991). ''Discus Fish'', p. 15. Barron's Educational Serie. ISBN 0-8120-4669-2</ref>
