Mg addition

Greetings all:

Been lurking for a while, and though I would finally start putting in my
$0.02 occasionally.  Just a short note on the recent thread about Mg
addition to tanks, and a replication of Karen Randall's observations
about its effects on various species.  I began adding K2SO4 to my 40G
(pH 7.0, KH 5, 160W fluo., loam/vermiculite sub, DIY CO2) a few months
ago, and noticed an improvement in growth and general plant appearance. 
About one month ago, I switched to full-blown PMDD with MgSO4.  Result:
Echinodorus spp. took off, growing out of the tank; C. wendtii looking
better; Rotala indica indifferent; H. difformis showing deformation and
curling of new leaves; Lilleaopsis spp. stopped growing and is getting
overgrown with hair algae.  Hair algae on Echinodorus and C. wendtii
decreased noticeably.  A few horticulturalist friends looked at my
plants and said that symptoms were similar to nitrogen or magnesium
overfertilization in fast growing terrestrials.  Unscientific
explanation is that they are essentially outgrowing themselves at the
new leaves due to excess nutrient.  I'm working on the scientific part
:).  Currently, I am trying to find a happy medium of fertilization
quantity that satisfies all of my plants.  One question:  I am pumping
quite a bit of SO4-- into the tank with the K2SO4 and MgSO4.  What does
this ion do when in the tank, and do I need to be concerned about its
buildup?  I do 25% water changes at least weekly.  
							D. Gauthier