Question
is it ok to put bone meal that has small amounts of nitrogen in it on my water hyacinths in my koi pond?  i have 6 or 7 beautiful butterfly koi, and i want the hyacinths to bloom but dont want to harm my fish.

Answer
I wouldn't do it.  If you pond is large enough, it probably won't hurt the fish but probably won't do much for the water hyacinth either.  Most ponds have plenty of nitrogen in the form of ammonia and nitrate.  The addition of nitrogen will probably just result in feeding algae growth.  Often, potassium is what's missing for water hyacinth to do well.  The easiest way for a non-chemist to add this is with the product Tetra FloraFin.  It has potassium in it.  It's not as cheap as adding potash or other chemicals but you have to careful doing that.  Also, koi will eat the roots off of water hyacinth.  You're more likely to get flowers if you protect some from the koi and also constrain the water hyacinth to a small area (they bloom when they think they're out of room) such as a hoop made from an old garden hose.

Here is the manufacturers page for Florafin:
http://www.tetra-fish.com/catalog/product.aspx?id=134

Here is one of many places that sells it:
http://www.thatpetplace.com/Products/KW/florafin/Class//T1/W34+0393+0376/EDP/760...