Is that because they contain phosphate?

IME, it's not really the phosphate that's the problem with Jobe's spikes. It's
the nitrogen. Some of it is in toxic forms, like ammonium and urea.

I'm
pretty interested in this subject because I am fighting hair algae in
a 10 gallon tank that I've been experimenting with. I am also having
problems getting a Nymphae lotus (zenkeri) growing. My thought was
that root tabs might encourage it to grow.

It's going to get much too big for a 10 gallon tank. You might be better off
starving it and stunting its growth. g

I've found that root tabs are necessary with Nymphaea. They are such nutrient
hogs. If you have one in the tank, you must feed each plant individually (with
root tabs) or the lotus will suck up nutrients as fast as you add them, and the
other plants will suffer.


Leigh

http://www.fortunecity.com/lavender/halloween/881/