Many fertilizer spikes get their nitrogen source from anhydrous ammonia, which as we all know is quite toxic to fish. (I almost killed my fish using a brand of spike recommended in rec.ponds) If you are not absolutely certain of the chemical make up of the spike I would not use it. By certain I mean read the label yourself ...

update .. checked while at the hardware store earlier.. Jobe's Tomato Spikes list nitrogen from Ammoniacal Nitrogen at 4.2%

So score them a NO ...

This post was edited by ajames54 on Fri, Mar 7, 14 at 14:59

Keith,
I know some people use them. I have read that on here too.
Honestly, you really don't need them.
If you have fish, even feeder fish like I have, you don't need them because the fish will create fertilizier for them.
I don't feed my fish, but if you did, you would definately have plenty of fertilizer.
I think the water turns green faster when you put fertilzier on your pond plants.
SOme people dip them in a seperate tub with Miracle grow in it, then after a couple hours return them to the pond.
I think you are better off not using anything, let the fish take care of it.
My plants bloom every year.

I've been using Jobe's tomato spikes in my water plants for nearly a decade with no harm to my fish. Also, fish poop may be good fertilizer but it won't get down into the pot where the roots are, so i don't see how it could help my plants. No need to argue the merits of fertilizing any plant vs. not frertilizing. Human beings figured that out long, long ago.