Some of the forumers said that this sera cryptopur work great in marine aquariums with invertebrates. Cos it does not contain any copper ! It is also excellently suitable for combating gill flukes!
This is what it cliam " The new treatment developed by sera‘s research laboratory is free from copper and is excellently tolerated by invertebrates. Even delicate sea cucumbers, shrimps, starfish, snails and sea urchins do not show any reaction to sera cryptopur. Some corals will, however, close their polyps for a short time, but they open again after the treatment without any damage."