I'm having trouble with some deficiency - trying to track it down. The only plants that seem to be affected are ludwigia arcuata and ammania gracilis. Heres a picture of the ludwigia.. http://www.aquaticscape.com/offsite/ludwigia.jpg In Ammania graclilis, on SOME stems the growing tip is crumpled. I'm thinking calcium - but I do have some crushed coral in my filter. Any ideas?