For excretion, uricotelic animals need

Ammonia is the most toxic form and requires large amount of water for its elimination. Urea is less toxic and requires moderate amounts of water for its elimination. Uric acid, being the least toxic, can be removed with a minimum loss of water. There is no need of expenditure of energy for the excretion of ammonia. Excretion of uric acid requires more expenditure of energy than excretion of urea.