( ( ( Low levels ) ( of ( salt concentration ) ) ) ( ( ( are also ) ( used ( by ( ( fish keepers ) ( who ( ( ( maintain ( their ( fresh ( water fish ) ) ) ) ( in ( ( tanks or ) ponds ) ) ) ( where ( ( no ( biological balance ) ) ( is attempted ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Low) (NNS levels)) (PP (IN of) (NP (NN salt) (NN concentration)))) (VP (VBP are) (ADVP (RB also)) (VP (VBN used) (PP (IN by) (NP (NP (NN fish) (NNS keepers)) (SBAR (WHNP (WP who)) (S (VP (VBP maintain) (NP (PRP$ their) (JJ fresh) (NN water) (NN fish)) (PP (IN in) (NP (NNS tanks) (CC or) (NNS ponds))) (SBAR (WHADVP (WRB where)) (S (NP (DT no) (JJ biological) (NN balance)) (VP (VBZ is) (VP (VBN attempted)))))))))))) (. .)))
Low levels of salt concentration are also used by fish keepers who maintain their fresh water fish in tanks or ponds where no biological balance is attempted.
(ROOT (S (NP (JJ Fresh) (NN water) (NNS biomes)) (VP (VBP are) (VP (VBN defined) (PP (IN by) (NP (JJ low) (NN salt) (NN concentration))))) (. .)))